U.S. patent number RE31,005 [Application Number 06/098,928] was granted by the patent office on 1982-08-03 for resilient plastic piston ring.
This patent grant is currently assigned to Ramsey Corporation. Invention is credited to Harold E. McCormick, Herbert F. Prasse.
United States Patent |
RE31,005 |
Prasse , et al. |
August 3, 1982 |
Resilient plastic piston ring
Abstract
A plastic ring for internal combustion engine pistons. In a
preferred embodiment, the ring has a flat outer diameter adapted to
engage the inner diameter of a compression piston ring and an inner
diameter adapted to engage the backwall of the ring groove. An
axial groove slightly spaced from the outer diameter extends into
the ring from the top thereof, whereby combustion gases will expand
the ring so that it acts as a circumferential expander for the
compression ring while preventing blowby of gases through the ring
groove. In another modification, the ring is used with its outer
diameter acting against the cylinder wall.
Inventors: |
Prasse; Herbert F. (Town and
Country, MO), McCormick; Harold E. (Ballwin, MO) |
Assignee: |
Ramsey Corporation (St. Louis,
MO)
|
Family
ID: |
26688402 |
Appl.
No.: |
06/098,928 |
Filed: |
November 30, 1979 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
016278 |
Mar 4, 1970 |
03608911 |
Sep 28, 1971 |
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Current U.S.
Class: |
277/446; 277/436;
277/453; 277/468; 277/488; 277/944 |
Current CPC
Class: |
F16J
9/06 (20130101); F16J 9/28 (20130101); F16J
9/066 (20130101); F16J 9/206 (20130101); F16J
9/063 (20130101); F05C 2225/04 (20130101) |
Current International
Class: |
F16J
9/06 (20060101); F16J 9/00 (20060101); F16J
9/26 (20060101); F16J 9/28 (20060101); F16J
9/20 (20060101); F16J 009/00 (); F16J 009/20 () |
Field of
Search: |
;277/138,139,140,141,27,192,193,58 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Smith; Robert I.
Attorney, Agent or Firm: Yount & Tarolli
Claims
We claim as our invention: .[.1. A piston and piston ring
combination for use in internal combustion engines comprising a
piston having a plurality of ring grooves therein, a plurality of
piston rings in said grooves, at least one of said piston rings
having its inner diameter spaced from the inner diameter of a ring
groove, a plastic piston ring positioned radially interiorly of
said piston ring in the groove, said plastic piston ring comprising
an annular ring of plastic material having inner and outer
diameters and an axial thickness, an axially extending groove
extending into said plastic piston ring from the top thereof, said
axial groove terminating in spaced relation to the bottom of the
said plastic piston ring, said groove dividing said ring into
radially inner and radially outer spaced-apart portions in the area
of the axial groove, the outer diameter of the radially outer
portion abutting the inner diameter of the said one piston ring,
the radially outer portion of the said plastic piston ring having
an axial height less than the axial height of the said ring groove,
and the said radially outer portion movable with respect to the
radially inner portion in dependent response to the presence of a
high pressure in the said axial groove..]. .[.2. The combination of
claim 1 wherein the said plastic piston ring is a 360.degree.
continuous ring..]. .[.3. The combination of claim 2 wherein the
said plastic piston ring is constructed of a polyimide resin which
is structurally stable at a temperature greater than 500.degree.
F..]. .[.4. A piston and piston ring combination for use in
internal combustion engines comprising: a piston, at least one ring
groove in said piston, said ring groove having a metal split piston
ring received therein, said metal piston ring having an axial
height less than the height of the ring groove, a plastic piston
ring concentric with said metal ring groove, a plastic piston ring
concentric with said metal ring received in said ring groove
radially interiorly of said metal ring, said plastic piston ring
being substantially U-shaped in cross section with the opening of
the U extending upwardly, the outer diameter leg of the said U
having an axial height less than the axial height of the ring
groove, the inner diameter leg of the said U having an axial height
greater than the outer diameter leg, said plastic piston ring
bottomed in the said ring groove, the radially outer leg of the
plastic piston ring circumferentially contacting the inner diameter
of the said metal piston ring and the said radially outer leg
movable with respect to the said radially inner leg in dependent
response to the presence of pressure in the opening of the said
U-shaped ring, whereby high-pressure gases entering the ring groove
above the said metal piston ring will enter the said opening and
press the inner diameter leg into sealing engagement with the
bottom of the ring groove and the outer diameter leg into sealing
engagement with the inner diameter of the metal piston ring thereby
entrapping the said gas in the said ring groove..]. .[.5. The
combination of claim 4 wherein the outer diameter of the said
plastic piston ring is circumferentially curved in an axial
direction..]. .[.6. The combination of claim 4 wherein the outer
diameter of the said plastic piston ring is circumferentially
tapered in an axial direction..]. .[.7. The combination of claim 4
wherein the inner diameter of the said plastic piston ring is
axially tapered..]. .[.8. The combination of claim 4 wherein the
inner diameter of said plastic piston ring is axially curved..].
.[.9. A piston and piston ring combination for use in internal
combustion engines comprising: a piston having at least one ring
groove therein, a plurality of axially thin split annulus piston
rings received in said groove projecting radially beyond said
groove, said piston rings positioned one atop the other in said
groove, the inner diameters of said piston rings terminating in
spaced relationship to the bottom of said groove, a plastic piston
ring received in said groove radially inwardly of said metal piston
ring, the said plastic piston ring having its inner diameter
bottomed on the bottom of the ring groove and its outer diameter
contacting the inner diameters of the said metal piston rings, an
axially extending groove projecting into the said plastic piston
ring intermediate the inner and outer diameters thereof, the said
axial groove projecting into the said ring from the top axial end
thereof and terminating in spaced relationship to the bottom axial
end thereof, the said plastic piston ring resilient whereby the
outer diameter is movable with respect to the inner diameter in
dependent response to the presence of high pressure fluid in the
said axial groove..]. .[.10. The combination of claim 9 wherein
portions of the material of the said plastic piston ring extend
from its outer diameter into the gaps in the split annulus metal
rings, the said gaps being circumferentially spaced from one
another whereby the said metal rings are restrained against
independent rotation with respect to one another..]. .[.11. The
combination of claim 10 wherein the said plastic piston ring is a
360.degree. continuous ring constructed of a high-temperature
plastic..]. .[.12. The combination of claim 10 wherein the plastic
piston ring has a radial groove in the ring from its inner
diameter, the said ring groove positioned intermediate the axial
ends of the said plastic piston ring..]. .[.13. The combination of
claim 12 wherein the said plastic piston ring has a second axial
extending groove positioned intermediate the inner and outer
diameters thereof extending into the ring from the bottom axial end
thereof and the said radial groove and axial groove bottom in
spaced relationship from one another..]. .[.14. In an internal
combustion engine having at least one piston reciprocatingly
positioned in a cylinder, the piston having ring grooves
therearound with metal piston rings therein, the improvement of at
least one of said grooves having a plastic piston ring received
therein positioned radially interiorly of the metal piston ring,
said plastic piston ring being resilient and having a
pressure-receiving axial groove therein, the plastic piston ring
being responsive to the presence of pressures in said ring groove
radially behind the said metal ring by sealing contact between the
plastic piston ring and the backwall of the ring groove and inner
diameter of the metal ring..]. .Iadd. 15. A piston and piston ring
combination for use in an internal combustion engine comprising a
piston movable in opposite directions in a cylinder and having at
least one ring groove therein, a plurality of axially thin metal
piston rings received in said groove one atop the other and
projecting radially beyond said groove, each piston ring being
split axially so as to have a circumferential gap, the gaps in said
piston rings being circumferentially spaced, radially inner
peripheries of said piston rings terminating in spaced relationship
to a radially inner periphery of said groove, an expander ring for
sealingly engaging the inner periphery of said groove and for
sealingly engaging the inner peripheries of said piston rings and
for restraining said piston rings against independent rotation with
respect to one another during movement of the piston in said
opposite directions, said expander ring comprising a one-piece body
of elastomeric material that is stable at temperatures up to at
least 900.degree. F. which may be present in an internal combustion
engine during its operation, said expander ring body having a
radial cross-section which includes an annular radially inner
portion to sealingly engage said radially inner surface of the
groove in the piston, an annular radially outer portion to
sealingly engage radially inner surfaces of the piston rings and
providing a single annular area of sealing engagement with the
inner surfaces of the piston rings which spans each joint between
abutting radially extending side surfaces of the piston rings and
an annular connector portion which is disposed between and connects
said inner and outer portions of said expander ring body, an
axially extending groove projecting into said expander ring
intermediate the inner and outer diameters thereof, the said axial
groove projecting into said ring from the top axial end thereof and
terminating in spaced relationship to the bottom axial end thereof,
said expander ring having an axial extent which is at least as
great as a major portion of the combined axial extents of the
piston rings so that said single annular area of sealing engagement
will have an axial extent which is at least as great as a major
portion of the combined axial extents of the inner surfaces of the
piston rings and said expander ring will be extruded radially into
the gap in each piston ring to hold each piston ring against
circumferential movement relative to the other. .Iaddend..Iadd. 16.
A piston and piston ring combination of claim 15 wherein the said
expander ring is a 360.degree. continuous ring. .Iaddend..Iadd. 17.
A piston and piston ring combination as defined in claim 15 wherein
said annular area of sealing engagement is cylindrical and extends
from axially opposite edges of said annular radially outer portion.
.Iaddend. .Iadd. 18. A piston and piston ring combination as
defined in claim 15, 16 or 17 wherein a radially extending
cicumferential groove is formed in the radially inner portion of
the expander ring body intermediate radially inner axial ends of
said expander ring, said circumferential groove opening toward the
bottom of the ring groove. .Iaddend..Iadd. 19. A piston and piston
ring combination as defined in claim 15, 16 or 17 wherein the
expander ring is constructed of a polyimide resin. .Iaddend..Iadd.
20. A piston and piston ring combination for use in an internal
combustion engine, comprising a piston movable in opposite
directions and having at least one ring groove therein, a plurality
of axially thin metal piston rings received in said groove one atop
the other and projecting radially beyond said groove, each piston
ring being split axially so as to have a cicumferential gap, the
gaps in said piston rings being circumferentially spaced, radially
inner surfaces of said piston rings terminating in spaced
relationship to the bottom of said groove, a continuous annular
expander ring received in said groove radially inwardly of said
piston ring, said expander ring being formed from a resilient high
temperature plastic stable at temperatures from 500.degree. F. to
900.degree. F. encountered in an internal combustion engine and
having a radially inner surface sealingly bottomed on said bottom
of the ring groove and a radially outer surface contacting the
inner surfaces of said piston rings, a first annular groove
projecting axially into said expander ring intermediate the
radially inner and outer surfaces thereof from a top axial end
thereof and terminating in spaced relationship to a bottom axial
end thereof thereby to provide radially inner and radially outer
portions of the expander ring, a radial groove formed in the
radially inner surface of the expander ring intermediate the axial
ends of said ring, a second axially projecting annular groove
positioned intermediate the radially inner and radially outer
surfaces of the expander ring and extending into the ring from the
bottom axial end thereof, said radial groove and axially projecting
grooves terminating in spaced relationship from one another, the
radially outer surface of said expander ring being a continuous
cylindrical surface for sealing engagement with the inner surfaces
of the piston rings and spanning each joint between abutting
radially extending surfaces of the piston rings, said cylindrical
outer surface having an axial extent which is substantially the
same as the combined axial extent of the inner surfaces of said
piston rings, and portions of the material of the said expander
ring extending from the outer surfaces of the expander ring into
the gaps in the split piston rings whereby said piston rings are
restrained against rotation with respect to one another. .Iaddend.
.Iadd. 21. A piston and piston ring combination as defined in claim
20 wherein said expander ring is constructed of a polyimide resin.
.Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to internal combustion engines and more
particularly to a piston ring for use in such engines.
2. Prior Art
Recently, more emphasis has been placed upon controlling internal
combustion engine emissions. It has been determined that a
significant quantity of undesirable emissions as well as power loss
are the result of combustion blowby. Such blowby occurs between the
outer diameter of the piston and the cylinder wall. While
compression rings, carried by the piston in ring grooves, have been
used to seal this space, the prior art rings and ring sets do not
completely seal the firing chamber.
Blowby can still occur between the outer diameter of the piston
ring and the cylinder wall, or by a gas flow around the piston ring
in the ring groove. It has been suggested to overcome the first
form of blowby by placing expansion springs in the ring groove to
force the piston ring into tighter contact with the cylinder wall.
Such expansion springs, while helpful, increase the friction of the
piston ring against the cylinder wall at all times by applying a
continuous pressure to the inner diameter of the piston ring.
It has been further suggested that the piston ring be made
substantially L-shaped, as in the U.S. Pats. to R. S. Moore, No.
1,159,066 and Goetze, No. 2,844,424, with one leg of the L engaging
the cylinder wall while the other leg is retained in the ring
groove. In such constructions, the force of the entrapped
combustion gases is used to expand, circumferentially, the first
leg into tighter engagement with the cylinder wall. While such
rings may be effective in reducing blowby between the ring and the
cylinder wall, they are not effective in preventing the escape of
such gas through the ring groove. Further, because such rings are
historically of split annular construction, a considerable amount
of gas can escape in the area of the ring gap.
SUMMARY OF THE INVENTION
Our invention overcomes the disadvantages of the prior art by
providing a resilient plastic piston ring which utilizes the
pressure of the entrapped gas to expand the main piston ring into
tighter sealing engagement with the cylinder wall while at the same
time expanding a portion of the ring into greater sealing contact
with the ring groove walls whereby escape is prevented at both the
interface between the piston ring and the cylinder wall and the
interface between the ring and the groove walls. Because the ring
relies upon the pressure of entrapped gas to provide the expansion
force, friction is reduced during those portions of the engine
cycle while either the pressure retained is reduced, as during
exhaust, or where there is no pressure retained as during
intake.
In a preferred embodiment, the ring is slightly U-shaped with one
leg of the U being radially thinner and axially shorter than the
other. The ring is bottomed in the ring groove and is utilized as a
backing for a standard piston ring. The opening of the U opens
axially upwardly and compressed gases seeking exit through the ring
groove will be forced into the bight resulting in a radial
expansion of the ring by pressing the legs of the U further apart.
This will at the same time seat the ring more firmly against the
backwall and bottom wall of the ring groove while increasing its
expansion pressure against the piston ring.
In another preferred embodiment, the expansion ring has grooves in
both the top and bottom faces and a circumferential groove in the
internal diameter face. The external diameter face is planar and
abuts the internal diameter of a standard composition piston ring
or of a ring pair.
In yet another embodiment, the resilient plastic piston ring of
this invention is used without a standard piston ring and has its
outer diameter adapted to contact the cylinder wall. The ring is
seated against the bottom of the ring groove and is preferably used
in a groove immediately adjacent the top of the piston to control
blowby or may be used in a lower groove, in an inverted position,
to function as an oil control ring.
In yet another embodiment, the ring is bottomed in the ring groove
and has a slanted outer diameter face adapted to engage the
cylinder wall, a portion of the outer periphery extending below the
normal ring groove depth in a secondary curved cutback groove.
In each instance the ring is preferably made of a high-temperature
resilient plastic such as Vespel (Reg. trademark of E. I. du Pont
de Nemours & Co. for a polyimide resin), Teflon (Reg. trademark
for a polytetrafluoroethylene manufactured by E. I. du Pont de
Nemours & Co.), or one of the high-temperature aromatic
polyimides. Although the ring is preferably a 360.degree.
continuous ring, specific materials may require the use of a split
ring for specific applications.
In those instances where the plastic ring does not contact the wall
of the combustion cylinder, in addition to the above-mentioned
high-temperature plastics, a high-temperature fluoroelastomer may
be used such as Viton (Reg. trademark of E. I. du Pont de Nemours
& Co. for a fluoroelastomer).
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the invention will be
readily apparent from the following description of certain
preferred embodiments thereof, taken in conjunction with the
accompanying drawings, although variations and modifications may be
effected without departing from the spirit and scope of the novel
concepts of the disclosure, and in which:
FIG. 1 is a fragmentary cross-sectional view of the piston ring of
this invention illustrating the ring seated in a ring groove behind
a standard compression piston ring.
FIG. 2 is a view similar to FIG. 1 illustrating a different ring
used in connection with a keystone piston ring.
FIG. 3 is a top plan view of a modified piston ring of this
invention.
FIG. 4 is a partially sectional side plan view of the FIG. 3
embodiment of the ring of this invention.
FIG. 5 is a cross-sectional view of the ring of FIG. 3, taken along
the line V--V.
FIG. 6 is a fragmentary cross-sectional view of the ring of FIGS.
3, 4 and 5 received in a piston ring groove and used as an
expansion ring for a pair of standard composition piston rings.
FIG. 7 is a fragmentary cross-sectional view of a piston equipped
with one of the embodiments of the ring of this invention.
FIG. 8 is a view similar to FIG. 7, illustrating the ring of FIG. 1
as received in a piston.
FIG. 9 is a cross-sectional view of the embodiment illustrated in
FIG. 7.
FIG. 10 is a fragmentary cross-sectional view of the ring area of a
piston received in a cylinder, illustrating one embodiment of the
continuous ring of this invention utilized for blowby control.
FIG. 11 is a top plan view of the ring illustrated in FIG. 10.
FIG. 12 is a fragmentary enlarged cross-sectional view of the top
ring groove of FIG. 10, illustrating the ring.
FIG. 13 is a fragmentary cross-sectional view of the ring grooves
of a modified piston illustrated as received in a cylinder wall and
showing other combination uses for the ring of the invention.
FIG. 14 is a fragmentary cross-sectional view of a ring groove of a
modified piston received in the cylinder, illustrating another
embodiment of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 8 fragmentarily illustrates a piston 20 of the type such as is
used in internal combustion engines, especially diesel engines and
the like. The piston 20 has a head portion 21 equipped with a
plurality of circumferential grooves 22, 23, 24 and 25. The grooves
receive piston rings which project outwardly therefrom to provide a
seal between the piston and the cylinder in which the piston is
received. The rings may be of the compression type such as the
rings 26, 27, and 28 or may be oil control rings such as the ring
29.
In the view illustrated, the ring 26 is illustrated as being a
torsion twist keystone ring received in a wedge-shaped groove, the
ring 27 is illustrated as being a conventional rectangular
compression ring with a coated wear face received in a rectangular
groove 23, and the ring 28 is illustrated as being a bevelled-faced
compression ring with a wear coated face also received in a
rectangular groove 24. The oil control ring 29 illustrated is a
one-piece U-shaped ring expanded by a circumferentially expanding
spring 30.
Although many advances have been made in the design of the piston
rings, with the increasing use of high-performance engines and the
increasing combustion pressures encountered therein, conventional
piston rings still allow a significant amount of combustion gases
to escape from the combustion area by traversing the path between
the piston head and cylinder wall. Some of this escapage occurs
between the outer diameter of the rings and the cylinder wall. A
large amount also occurs by passage of gas around the piston ring
in the ring groove. It is the purpose of this invention to minimize
such gas blowby.
In order to effectuate this purpose, in the embodiment illustrated
in FIG. 8, a plastic piston ring 31, according to this invention,
is placed in a ring groove behind the conventional piston ring. The
ring 31 is illustrated as being placed in the ring groove 23 behind
the compression ring 27.
FIG. 1 is an enlarged fragmentary view of the ring groove 23 and
rings 27 and 31. In accordance with the customary practice, the
groove is axially taller and radially deeper than the conventional
piston ring 27 so that the ring may be movable therein.
The ring 31 is positioned radially inwardly of the ring 27, and is
preferably bottomed against the backwall 34 of the groove 23. The
radially inner portion 35 of the ring preferably has a axial height
approximately the same as the axial height of the groove 23. The
front or outer diameter face 36 of the ring rides against the inner
diameter 37 of the ring 27 and has an axial height less than the
axial height of the inner diameter portion 35. An axially extending
groove 38 projects into the ring between the radially outer portion
39 and the radially inner portion 35 with the inner portion being
slightly thicker in a radial direction than the outer portion.
The groove 38 tapers axially upward and radially outward to a point
40 either at or in close-spaced relation to the radially outer face
36. .[.It is to be understood that although the ring 31 is
illustrated as having its radially inner portion 35 thicker than
the radially outer face 36..]. It is to be understood that although
the ring 31 is illustrated as having its radially inner portion 35
thicker than the radially outer portion 39, the two being separated
by the groove 38, that this is a matter of design and that in
specific embodiments the thicknesses may be varied. Further, it is
to be understood that the dimensions of the rings 31 are set so
that it may be inserted into the ring groove behind the compression
ring 27 in such a manner that it will not adversely affect correct
installation of the ring 27. It will further be understood that the
ring 31 may be assembled with a clearance relationship between its
innner diameter and the backwall of the groove or between its outer
diameter and the back of the ring 27 so as to allow the ring 27 to
be compressed when inserted into the cylinder. In this manner, the
normal circumferential expansion force of the ring 27 against the
cylinder wall is preserved.
The ring 31 is constructed of a high-temperature plastic and
preferably of plastics such as the polyimides which are relatively
stable at the temperature encountered in an internal combustion
engine. An acceptable plastic for use in constructing the ring 31
is known as Vespel, a registered trademark of the du Pont
corporation. Such plastics are capable of continuous operation of
temperatures of up to 500.degree. F. and intermittent temperature
exposures up to 900.degree. F.
The ring is preferably constructed of material which has an elastic
memory so that the ring may be constructed as a continuous
360.degree. ring. When so constructed, the ring is stretched to be
fittable over the piston head and thereafter shrunk to its normal
diameter within the ring groove. In lower ring groove applications,
plastic materials such as Teflon (a registered trademark of the E.
I. du Pont de Nemours & Co.) may be utilized. Where the elastic
memory of the material is such as to be undesirable for the
stretching and shrink fit insertion into the ring groove, the ring
may be split to facilitate installation. It is to be understood
that although different materials may be used, the preferred
material is a material such as Vespel or Viton. Viton is a
fluoroelastomer which in commercial embodiments such as Viton A or
Viton B exhibits the desired properties of high-temperature
stability and flexibility. Further, the material must be resilient
at the operating temperatures encountered in the ring groove and
should have self-lubricating properties.
In the absence of pressure acting on the ring 31, the ring exerts
little cicumferential expansion force against the compression ring
27. However, during combustion, high-pressure gases flow into the
ring groove 23 as illustrated by the arrows 40. The high-pressure
gas will flow into the groove 38 where it will act equally against
the radially inner wall of the groove 42, the radially outer wall
of the groove 44 and the bight of the groove 43. This action will
cause an expansion of the resilient material ring by increasing the
radial depth of the groove. In this manner, the radially inner
portion 35 will be pressed into tighter engagement with the bottom
of the ring groove to prevent escape of compression gas around the
inner diameter of the ring 31. The action of the gas against the
bight portion 43 of the groove will force the ring 31 into tighter
sealing engagement with the bottom wall 45 of the ring groove,
thereby aiding in preventing flow of the compression gas around the
ring 31. The pressure of the gas against the outer diameter wall 44
of the groove will act to force the outer diameter wall 36 of the
ring 31 against the inner diameter wall 37 of the compression ring
27. This will create a circumferential expansion force against the
compression ring 27 to increase the sealing pressure between the
compression ring and the cylinder wall. This pressure also
increases the sealing pressure between the outer diameter wall 36
of the ring 31 and the inner diameter wall 37 of the ring 27,
thereby preventing flow of gas between the two rings.
It can therefore be seen that the compression gases will be
effectively trapped within the ring groove in such a manner that
leakage paths within the groove are blocked by a sealing force
which is proportionate to the pressure of the gas. This will reduce
or eliminate blowby through the ring groove while at the same time
reducing blowby between the compression ring face and the cylinder
wall by increasing the expansive force of the compression ring
against the cylinder wall in direct response to the increase of
compression gas pressure. Because the ring 31 is resilient, it is
able to accommodate the radial expansion caused by relative
movement between the radially inner portion 35 and the radially
outer portion 39. Further, due to its resiliency, when the pressure
of the compression gases is reduced, as during the intake cycle of
a four-cycle engine, the ring 31 will resume its initial shape
reducing circumferential force against the compression ring 27 and
thereby lessening friction between the compression ring 27 and the
cylinder wall.
FIG. 2 illustrates another embodiment of the ring 31. The ring 51
illustrated in FIG. 2 is shown fitted into a wedge-shaped groove 52
which receives a keystone ring 53. The ring 51, as the ring 31, is
received radially inwardly of the compression ring 53. The ring 51
also has a central axial groove 54 extending into the ring from the
top thereof. The radially inner wall 55 of the ring 51 is angled
axially upward and radially inward to provide a sloping backface.
The radially outer diameter face 56 of the ring is curved to give
the ring a barrel face contour. The combination of the slanting
backface 55 and the curved barrel face 56 allows the ring 51 to
effectively seal the ring groove 52 with minimal normal contact
between the ring 51 and the walls of the ring groove and the inner
diameter of the compression ring. Further, due to the resiliency of
the material of the ring 51 and the slanting inner diameter face 55
and barrel-shaped outer diameter face 56, the ring does not exert
as large a circumferential expansion force as does the ring
illustrated in FIG. 1. Further, some of the force of the
compression gases may be utilized in deforming the inner peripheral
portion 57 of the ring 51, thereby reducing the space 58 between
the slanted face 55 and the bottom of the ring groove.
FIGS. 3 through 6 illustrate another embodiment of the plastic
piston ring of this invention. The ring 61 has both top 62 and
bottom 63 axial grooves. There is also an inner diameter groove 64
extending radially into the ring from the backface thereof. The
outer diameter face 64 is axially straight and is designed to mate
with the inner diameter of a conventional compression ring or
rings.
Conventional piston rings have a radial gap therein to allow
insertion into the piston ring groove. Such gaps provide an escape
path for combustion gases. In order to close this gap, it has been
suggested to place two axially thin compression piston rings in a
single ring groove with their gaps circumferentially spaced from
one another. However, during operation of the piston, the piston
rings may move independently of one another and their gaps
thereafter become aligned. When this occurs, the compression gases
may escape axially through the aligned gaps.
The plastic piston ring 61 retains the circumferential misalignment
of such rings. As illustrated in FIG. 6, the ring 61 is placed
radially inwardly of two conventional compression rings 67 and 68.
The radially outer face 65 of the ring 61 abuts the inner diameter
faces 69 of the compression rings 67 and 68. Because the ring 61 is
made of a plastic material, portions of its outer diameter face 65
will extrude into the gaps 70 as illustrated in FIG. 3. The
extrusion points 71 will lock the ring gaps 70 in circumferential
misalignment and thereafter the piston rings 67 and 68 and the ring
61 will move in the groove 72 as a unit.
The ring 61 further acts to prevent compression gas blowby through
the ring groove 72. As high-pressure gas enters the ring groove 72,
as illustrated by the arrows 73, it will be trapped in the upper
portion of the groove 72 by the ring 61. As the high-pressure gases
contact the ring, they will enter the groove 62 acting against the
radially inner portion 75 to force the inner diameter walls 76 and
77 against the backwall 78 of the ring groove. At the same time,
they will increase the circumferential expansion force of the outer
diameter wall 65 against the inner diameters 69 of the rings 67 and
68. Due to the provision of the three grooves 62, 63 and 64, the
ring 61 is slightly compressible in both an axially downward and
radially inward direction. Further, the presence of high-pressure
gas in the groove 62 will force apart the radially inner portion 75
and the radially outer portion 79 of the ring 61 thereby creating
both the sealing force against the backwall 79 and the expansion
force against the compression rings 67 and 68. In this manner, the
gas will be trapped in the ring groove. An additional feature is
provided by grooving both the top and the bottom axial ends of the
ring 61 in that the ring may be inserted in the ring groove with
either of the grooves 62 or 63 on the top.
FIGS. 7 and 9 illustrate another modification of the ring of this
invention which is inserted in an especially cut ring groove. The
ring 90 has an outer diameter face 91 adapted to contact the
cylinder bore wall, thereby providing an oil scraping lip.
The ring has a radially inner axially extending portion 93 which is
integral with a radially outer portion 94 through the radially
extending bottom portion 95. A groove 96 extending into the ring
from the top thereof separates the inner portion 93 from the outer
portion 94. The top 97 of the radially outer portion at the front
face 91 is below the top 98 of the radially inner portion and the
axial top surface of the radially outer portion 94 has an arcuate
slope from the point 97 to the groove 96. The bottom 99 of the ring
90 extends radially outward from the backwall 100 to a point 101
beyond the groove 96. Thereafter, the bottom tapers arcuately
axially downward and outward to the front face 91 so that the
bottom portion of the radially outermost portion 94 extends axially
beyond and below the remainder of the ring. The scraping face 91 is
tapered radially inward from the bottom 102 to the top 97
thereof.
The piston groove 105 is a rectangular groove having a height
slightly greater than the height of the radially inner portion 93
of the ring 90. A secondary stacked portion 106 of the groove 105
receives the axially extended bottom portion of the radially outer
portion 94. The portion 106 of the groove is arcuately cut from the
bottom 107 of the rectangular groove at the outer diameter thereof.
The portion 106 is cut radially into the piston a distance slightly
less than the thickness of the lip portion 108 of the ring formed
by the bottom of the radially outer portion 94. In this manner, the
portion 108 projects out of the ring groove to a point where it may
contact the cylinder wall.
The backwall 100 of the ring 90 preferably bottoms against the
backwall 100a of the ring groove 105 in a manner substantially the
same as the ring 31 of FIG. 8.
When high-pressure compression gases flow into the ring groove 105
as illustrated by the arrow 109, they will encounter the groove 96
where they will press the face 91 against the cylinder wall. The
taper of the face 91 allows the axially upper portion of the ring
of be expanded against the cylinder wall when high-pressure gases
are present in the groove 96. The pressure of the compression gases
will also act in the groove 96 of the ring 90 to radially expand
the same whereby the backwall 100 of the ring 90 will be forced
into sealing engagement with the backwall 100a of the ring groove
105. The contact between the cylinder wall and the axially lower
portion of the scraping face 91 allows the ring to function as an
oil-scraping ring. The presence of high-pressure gases in the
groove 96 will increase the contact pressure between the face 91 of
the ring 90 and the cylinder wall. As the pressure in the groove 96
increases, the portion of the front face 91 of the ring 90
contacting the cylinder wall will increase as the ring 90 is
circumferentially expanded. In this manner the ring 90 functions as
an anti-blowby ring in that it seals escape paths through the ring
groove 105 by contact with the axial end walls of the ring groove
105 and by sealing engagement with the backwall 100a of the groove.
Further blowby between the piston head and the cylinder wall is
minimized due to expansion pressure contact between the outer
diameter face 91 of the ring 90 and the cylinder wall. In order to
aid in effectuating this seal, the ring groove 105 is preferably
equal to or just slightly greater than the height of the inner
diameter portion 93 of the ring groove 90 so that the top thereof
98 may contact the axial end of the ring groove in response to the
pressure of gases in the groove 96 when the backwall 100 of the
ring 90 is bottomed against the backwall 100a of the ring
groove.
FIGS. 10 through 13 illustrate another embodiment of the plastic
piston ring of this invention. FIG. 10 illustrates the ring 120
received in a special top ring groove 121 in a piston 122. A
portion of the ring rides against the cylinder wall 123.
The ring 120 is an annular continuous plastic piston ring having a
flat bottom or axial end 124 and a straight axially extending
backwall 125. An axially extending groove .[.126b.]. .Iadd.126
.Iaddend.projects into the ring from the top 127 thereof, dividing
the ring into a radially inner portion 128 and a radially outer
portion 129. The radially outer portion 129 terminates at its outer
diameter with a cylinder wall engaging portion 130. The axial top
end 131 of the radially outer portion 129 is below the top 127 of
the radially inner portion 128 and is spaced from the top sidewall
132 of the piston groove 121. The axial height of the ring 120 at
the radially inner portion is approximately the same as the height
of the groove. In this manner, the upper portion of the radially
outer portion serves as a sealing lip with the bottom axial portion
thereof cut back as at 134 to a reduced diameter portion so that
the cylinder engaging portion 130 projects radially beyond the
remainder of the ring.
The groove 121 is in close-spaced relation to the top 135 of the
piston 122 and is located above the normal position of the top ring
groove 136 of a standard piston. The ring 120 serves as an
anti-blowby ring reducing harmful exhaust emissions as well as
preventing entrance of uncombusted fuel and oxygen mixtures into
the space between the cylinder wall 123 and the piston 122 where
they would normally not be combusted due to the smallness of the
area.
In addition, the ring acts in the same manner as previously
described rings. As high-pressure combustion gases force their way
between the top of the piston and the cylinder wall, they are
entrapped in the groove 126 as indicated by the arrow 138. Their
effect upon the groove will be to force the inner diameter portion
128 tightly against the back 139 of the piston groove and to force
the bottom wall 124 of the ring against the bottom wall 140 of the
groove, thereby preventing escape of gases around the ring in the
groove. Further, they will force the cylinder wall engaging portion
130 of the outer diameter portion 129 tighter against the cylinder
wall 123 thereby cutting off the flow at the outer diameter. In the
absence of high-pressure gases in the groove 126, the contact
between the ring and the cylinder wall will be less thereby
reducing friction. Therefore, contact between the cylinder wiping
portion 130 and the cylinder wall 123 will be greatest during the
power and compression strokes and smallest during the intake
stroke. During the exhaust stroke, there will be a slight expansion
effect on the ring.
FIG. 13 illustrates a dual ring, dual groove arrangement where one
of the rings 150 identical to the ring 120 is inserted in a top
groove 151 identical to the groove 121. A secondary ring 152 which
may be identical to the rings 150 and 120, or which may be as
illustrated having a shallower groove 154, is inserted in a lower
ring groove 153. This ring acts as an oil control ring with the
cylinder engaging lip 155 acting against the cylinder wall 156 to
wipe excess oil therefrom and to prevent excess amounts of oil from
being forced upwardly to the upper reaches of the cylinder where
they could be combusted to form hydrocarbon deposits on the
cylinder wall.
FIG. 14 illustrates a single ring 158 received in a wider top
piston ring groove 159. The single ring 158 functions as a
combination of the rings 150 and 152 and has two axially spaced
cylinder engaging lips 160 and 161 separated by a reduced diameter
portion 162 which does not normally contact the cylinder wall. In
this embodiment, the lower lip 161 functions as an oil control lip
while the upper lip 160 functions in the manner of the cylinder
engaging portion 130 of the ring 120.
It can therefore be seen from the above that our invention provides
an improved plastic piston ring which reduces the exhaustion of
harmful internal combustion engine emission products by reducing
gas blowby between the piston and the wall of the cylinder in which
the piston operates. In some embodiments, the ring is placed behind
a standard combustion ring or ring set and transforms the axially
directed flow force of the combustion gases into a radial pressure
which seals the interior of the piston ring groove to prevent gas
blowby therethrough and which also increases the sealing
.[.contract.]. .Iadd.contact .Iaddend.between the compression ring
and the cylinder wall. In other embodiments, the ring can directly
engage the cylinder wall with a given standard pressure and in the
presence of high-pressure gases will contact the cylinder wall with
a greater pressure while at the same time sealing the groove in
which it is received to prevent internal groove blowby.
Although the teachings of our invention have herein been discussed
with reference to specific theories and embodiments, it is to be
understood that these are by way of illustration only and that
others may wish to utilize may invention in different designs or
applications.
* * * * *