A sealing mechanism positioned between a movable piston wall and stationary cylinder wall concentric therewith. The sealing mechanism includes a circumferential groove formed in one of the concentric walls, and an O-ring positioned in the circumferential groove, the O-ring having a diameter less than the axial length of the groove and being compressed between a pair of opposing surfaces, a first surface formed integrally on the floor of the circumferential groove and a second surface formed integrally on one of the concentric walls. At least one of the pair of opposing surfaces has at least one upstanding serration for engaging the O-ring and forcing the O-ring to rotate when it moves from side to side in the circumferential groove.

This invention relates to a sealing mechanism positioned between a movable 
piston wall and stationary cylinder wall concentric therewith. 
More particularly, the invention relates to a sealing mechanism positioned 
between a movable piston wall and stationary cylinder wall concentric 
therewith in which an O-ring is compressed between the cylinder wall and 
the floor surface of a circumferential groove formed in the wall of the 
piston. 
In another respect, the invention relates to a sealing mechanism positioned 
between a movable piston wall and stationary cylinder wall concentric 
therewith in which an O-ring is retained in a circumferential groove 
formed in the wall of the piston and moves from side to side in the groove 
when the piston is axially reciprocated in the cylinder. 
In a further and more specific respect, the invention relates to a fluid 
sealing mechanism of the type described in which the floor of the 
circumferential groove has upstanding serrations which force the O-ring to 
roll as it moves from side to side in the groove. 
Forming a seal by compressing an O-ring between a cylinder wall and the 
floor of a circumferential groove formed in an adjacent piston wall is 
well known in the art. The axial width of such circumferential grooves is 
often made greater than the diameter of the O-ring under the assumption 
that the O-ring will "roll" along the groove when the piston reciprocates 
in the cylinder. See for example U.S. Pat. Nos. 2,317,034 to Dalkin and 
2,394,364 to Christensen. However, as described in the Parker "O" Ring 
Handbook No. ORD-5700, under actual operating conditions the O-ring does 
not roll but instead slides from side to side in the groove during all but 
a small fraction of a reciprocating stroke of the piston. 
O-rings utilized in circumferential grooves having an axial width greater 
than the compressed axial diameter of the O-ring are susceptible to a 
phenomenon known as "spiral failure". Spiral failure occurs when some 
segments of the O-ring roll while other adjacent segments slide such that 
two adjacent portions of the O-ring are twisted in relation to one 
another. An excessive cumulative amount of twisting will cause the surface 
of the O-ring to rupture and eventually may result in a complete break or 
separation at some point along the O-ring. The occurance of such "spiral 
failure" can be minimized by insuring that the entire length of the O-ring 
rolls during its side to side travel in the groove. 
Rotation of the O-ring during its side to side travel in a circumferential 
groove is, of course, further desirable since such a rolling O-ring 
presents a new sealing surface to the wall of the cylinder with each 
reciprocation of the piston, thereby increasing the effective operational 
life and efficiency of sealing of the O-ring. 
One means developed to insure the rotation of the O-ring during movement of 
the piston is to compress the O-ring against an annular support member 
positioned in the groove. When the piston reciprocates the frictional 
contact of the O-ring with the wall of the cylinder causes the O-ring to 
rotate in the annular support member. See U.S. Pat. Nos. 2,738,803 to 
Manning, 3,466,054 to Berg and 3,806,136 to Warner, et al. A disadvantage 
of this approach is that machining or forming the annular member 
supporting and containing the O-ring requires additional time and expense 
in comparison to the conventional flat bottomed groove. In addition, the 
frictional force generated when a portion of the O-ring slides over the 
surface of the cylinder wall may not be sufficient to overcome the 
opposing frictional force between the O-ring and floor surface of the 
annular support member. In this case the O-ring would once again slide 
over the cylinder wall. 
Accordingly, it would be highly desirable to provide a sealing mechanism 
which would insure the rotation of an O-ring as it moved from side to side 
in a circumferential groove during reciprocation of the piston in the 
cylinder. 
Therefore, it is a principle object of the present invention to provide an 
improved sealing mechanism for use between a movable piston wall and 
stationary cylinder wall. 
A further object of the invention is to provide an improved sealing 
mechanism of the type in which an O-ring positioned in a circumferential 
groove formed in the wall of the piston rotates as it moves from side to 
side in the groove while the piston is axially reciprocated within the 
cylinder. 
Still another object of the invention is to provide an improved sealing 
mechanism of the type described which reduces the likelihood of spiral 
failure of the O-ring and increases the effective life and efficiency of 
sealing of the O-ring.

Briefly, in accordance with the invention, I provide an improved sealing 
mechanism for use between a movable piston wall and stationary cylinder 
wall concentric therewith. The sealing mechanism comprises a 
circumferential groove formed in one of the concentric walls, an endless 
annular elastic hose positioned in the circumferential groove and 
compressed between a pair of surfaces, a first surface formed on the floor 
of the circumferential groove, and a second surface formed on one of the 
concentric walls, the second surface generally opposing the first surface. 
The annular hose has a diameter less than the axial length of the 
circumferential groove. One of the pair of opposing surfaces has at least 
one upstanding serration for engaging the annular hose and forcing the 
hose to rotate when the hose moves from side to side in the 
circumferential groove. 
Turning now to the drawings, which depict the presently preferred 
embodiments of the invention for the purpose of illustrating the practice 
thereof and not by way of limitation of the scope of the invention, and in 
which like reference characters identify the same elements in the several 
views, FIG. 1 illustrates a piston 11 which reciprocates within cylinder 
walls 10 and along axis 15 and is provided with an O-ring 13 compressed 
between the floor of circumferential groove 14 and cylinder wall surface 
12. The axial width of circumferential groove 14 is greater than the 
compressed diameter of O-ring 13 so that O-ring 13 moves from side to side 
in groove 14 during the reciprocation of piston 11. Pressurized fluid 
entering through channels 17 reciprocates piston 11 along axis 15. 
As illustrated in FIG. 2, in the prior art both the floor 16 of groove 14 
and cylinder wall 12 were relatively smooth surfaces and O-ring 13 would 
slide from side to side in groove 14 as shown by arrows A when piston 11 
reciprocated in the directions of arrows B along axis 15. 
FIGS. 3-7 illustrate the presently preferred embodiments of the invention. 
In each embodiment at least one of the surfaces 12, 16 is provided with 
upstanding projections or serrations 20 which engage the O-ring 13 and 
force the ring 13 to rotate when piston 11 moves relative to cylinder 
walls 12. As demonstrated by FIGS. 3 and 4 serrations 20 may be 
triangular, rectangular, or take on a variety of other shapes. In 
addition, as would be appreciated by those skilled in the art, serrations 
20 need not be evenly spaced. Similarly, projections 20 could form a 
striated pattern on surfaces 12 and/or 16, could form a pattern of 
discrete upstanding points similar to those found in Braille, or could 
form numerous other patterns which would function to engage and force hose 
13 to rotate when piston 11 moved within cylinder wall 10. 
It is not necessary that the opposing surfaces 12, 16 compressing O-ring 13 
be parallel. For example, in FIG. 6 floor surface 16 of groove 14 is 
curved such that ring 13 is retained and rotates therein during movement 
of piston 11. 
In operation, as shown in FIGS. 3-7, movement of piston 11 in the direction 
of arrows C causes O-ring 13 to rotate in the direction of arrows D. 
O-ring 13 rotates in the direction of arrow E when piston 11 is displaced 
in the direction of arrow F. Serrations 20 force ring 13 to roll as ring 
13 moves from side to side in groove 14 of FIGS. 3, 5, 6 and 7 and force 
ring 13 to rotate in the annular groove 14 of FIG. 4. Rotation of O-ring 
13 presents a new sealing surface to the wall of the cylinder or piston 
with each reciprocation of the piston and increases the operational life 
and efficiency of sealing of the O-ring. Serrations 20 cause O-ring 13 to 
rotate at a relatively uniform rate along the entire length thereof. 
The embodiment of the invention shown in FIGS. 3-4, 8A-8E comprises a 
combination sliding-rolling seal. In high pressure applications a sliding 
seal is preferred because it prevents less fluid, i.e., gas or liquid, 
from bypassing the seal. A rolling seal tends to function like an ink 
roller and to carry, on the seal surface, fluid from the area containing 
pressurized fluid past the point(s) where the seal contacts the surface(s) 
being sealed and into areas not intended to receive or contain fluid. 
As shown in FIGS. 8A-8E, when O-ring seal 25 is in position against 
upstanding wall 29 of groove 30 and the piston in which groove 30 is 
formed is moving in the direction of arrow G while surface 26 remains 
stationary, O-ring seal 25 does not move and the portion of seal 25 
contacting surface 26 slides along surface 26. Teeth 27 maintain seal 25 
in fixed position against wall 29. In FIGS. 8A-8E, vertical line X and 
point Y where line X intersects stationary surface 26 are provided as 
fixed references to demonstrate the movement of groove 30 and seal 25 with 
respect thereto. 
After the piston containing groove 30 stops moving in direction G and 
reverses itself and begins moving in the direction indicated by arrow H in 
FIGS. 8B-8E, hose 25 begins rolling as indicated by arrow I in FIGS. 8B, 
8C. Teeth 27 generally insure that each portion rotates at the same rate 
as other portions of seal 25 and, consequently, tends to minimize the 
likelihood of spiral failure of the seal. 
After the piston in which groove 30 is formed begins moving in the 
direction indicated by arrow H in FIG. 8B, seal 25 continues to roll 
between toothed floor 27 of groove 30 and surface 26 (FIG. 8C) until seal 
25 abut against wall 28 of groove 30 as shown in FIG. 8D. As is depicted 
in FIG. 8E, after seal 25 rolls against wall 28, it remains stationary 
while the piston continues to move in direction H. Striations 27 prevent 
seal 25 from rolling while it is in position against wall 28 and the 
piston is moving in direction H. While seal 25 is fixed in position 
against wall 28 and the piston is moving in direction H, the portion of 
seal 25 contacting surface 26 slides along surface 26. When the piston 
stops moving in direction H and again begins moving in direction G, seal 
25 rolls across groove 30 to the position shown in FIG. 8A. Once seal 25 
reaches the position shown in FIG. 8A, it remains in that position and in 
sliding contact with surface 26 while the piston continues to move in 
direction G. 
In use of the embodiment of the invention shown in FIGS. 8A-8E, the width 
of groove 30 (the distance between the vertical lines representing walls 
28, 29 in FIGS. 8A-8E) is minimized so that seal 25 only rotates a 
relatively short distance when moving from wall 29 to wall 28 after the 
piston stops moving in direction G and begins moving in direction H. This 
minimizes the time the seal is rolling and allows seal 25 to primarily 
function as a sliding seal, which is, as earlier noted, desired in high 
pressure applications. However, the rolling feature of the seal, since it 
provides two different seal surfaces in sliding contact with surface 26, 
doubles the useful life of the seal. If striations 27 were not provided 
along the floor of groove 30 as shown in FIGS. 3, 4, 8A-8E seal 25 would 
be susceptible to spiral failure or would tend to simply slide back and 
forth in groove 30. Although the floor of groove 30 is pictured as being 
generally flat, i.e., striations 27 shown in the cross-sectional view of 
groove 30 in FIGS. 8A-8E generally lie along an imaginary line parallel to 
the line representing surface 26, it might be desirable to form the floor 
of groove 30 such that striations 27 generally lie along a sinuate or 
concave or convex line. 
As earlier noted, the word serration as used herein includes serrations, 
striations, deticulations and any other type, or shape of seal engaging 
projections or edges.