Oil ring assembly

An oil ring assembly comprising a pair of split rails and a piston ring spacer/expander on which said rails are mounted. Each rail is provided with a radially inwardly extending protrusion that lies substantially entirely within the thickness of the rail. The protrusion extends into and engages the spacer expander to limit the circumferential movement of the rail relative to the spacer/expander.

BACKGROUND AND SUMMARY OF THE INVENTION 
It is conventional to provide oil ring assemblies for internal combustion 
engines with two oil rails that are yieldingly urged radially outwardly 
into contact with the cylinder wall of an engine by a piston ring 
spacer/expander. It has been found by extensive testing that there is a 
tendency for the oil rings to move circumferentially so that the oil ring 
gaps align with each other and frequently with the gap of the 
spacer/expander. In such an occurrence, oil consumption of the engine is 
substantially increased. 
Past history has proven that there is a detriment to oil economy when the 
gaps of the two rails align circumferentially. The magnitude of this 
detriment has been measured in the range of 40% reduction in oil economy. 
There is, therefore, a need to lock the rotation of each rail relative to 
the expander in an installed staggered circumferential orientation. Prior 
art to accomplish this desired goal is represented in U.S. Pat. No. 
4,572,520. In this patent, two potential locking methodologies are 
presented. One presents an axial displacement of rail material to engage 
with the expander. This methodology, although effective, results in 
"directional" rails which must be oriented, whereby, the axial 
displacement of the top rail must be installed downward to engage the 
expander and the axial displacement of the bottom rail must be installed 
upward to also engage the expander. The second methodology presented in 
U.S. Pat. No. 4,572,520 presents a rivet feature which protrudes axially 
from the rail in both directions. This feature is "nondirectional"; 
however, the presence of the axial displacement on the rail towards the 
groove side requires the presence of a relief into the groove to accept 
the rivet head, as well as the need to orient the rail upon assembly, 
whereby the rivet head is circumferentially aligned with the groove 
relief. Additionally, this method results in the locking of rail rotation 
relative to the piston. Both methods require the proper orientation of the 
rail relative to the expander prior to the installation of the rail with 
the expander. These directional and/or circumferential orientation 
features present major inconvenience to the automated loading and 
circumferential staggering of the oil ring components. 
Prior art to accomplish component circumferential staggering of gaps for 
multiple piece compression ring assemblies exists as demonstrated in U.S. 
Pat. No. 3,391,942. In this patent, an expander ring is bent to form ribs 
that engage recesses on compression rings. Due to the multitude of 
components, with dimension stackups and the associated degree of 
difficulty in loading said components into compression groove, the 
assembly is economically prohibitive. 
Other oil ring patents exist (U.S. Pat. Nos. 3,184,245, 3,346,252 and 
3,105,695) which exhibit locking mechanisms to lock the rotation of the 
expander relative to the piston but do not restrict the rotation of the 
rails relative to the expander. 
Among the objectives of the present invention are to provide an oil ring 
assembly which obviates the aforementioned problems; which can be achieved 
at relatively low cost; which can be assembled readily without any 
possibility of misassembly; and which would be effective to eliminate any 
possibility of alignment of the gaps of the oil ring rails and the 
spacer/expander. 
An oil ring assembly embodying the invention comprises a pair of split 
rails and a piston ring spacer and expander on which said rails are 
mounted. Each rail is provided with a radially inwardly extending 
protrusion that lies substantially entirely within the thickness of the 
rail. The protrusion extends into and engages the spacer expander to limit 
the circumferential movement of the rail relative to the spacer/expander. 
A feature of the present invention is the fact that the locking force (to 
prohibit rotation of the rails independently relative to the expander) is 
energized by the tension generated by the expander upon compression of the 
assembly to bore diameter. This feature permits the ability to stagger the 
relative orientation of the expander and the rails after installation of 
the components into the oil ring groove but prior to compression of the 
assembly to bore diameter. This feature is important since some automated 
ring installation equipment installs the rails onto the piston groove 
aligned with each other and subsequent circumferential staggering is 
required and not possible with oil ring prior art U.S. Pat. No. 4,572,520. 
Another feature of the radial protrusion on the invention is that the rail 
is functionally axially nondirectional and no efforts must be expended to 
orient the rail's bump side up or bump side down as contrasted with the 
axial locking feature in the prior art U.S. Pat. No. 4,572,520. 
Another feature of the radial protrusion in this invention is that the rail 
incorporating this invention is compatible with any spacer/expander in 
which the circumferential gap between expander rail support contact pads 
is greater than or equal to the circumferential length of the radial 
protrusion on the rail. For example purposes only, the described expander 
per FIG. 1 shall be utilized in describing the invention.

DESCRIPTION 
Referring to FIGS. 1-5A, an oil ring assembly 10 embodying the invention 
comprises a pair of split rails 11 and a piston ring spacer/expander 12 on 
which said rails 11 are mounted. Each rail 11 is of generally circular 
construction with a gap 13 between the ends. The spacer/expander 12 
yieldingly urges the rails 11 outwardly into contact with the cylindrical 
wall 14 of a cylinder 15 of the internal combustion engine. Each rail 11 
is generally rectangular in cross-section and has a greater radial 
thickness than the axial thickness. 
In accordance with the invention, each rail 11 is provided with a radially 
inwardly extending protrusion 20 that lies substantially entirely within 
the thickness of the rail 11. The protrusion 20 extends into and engages 
one of the gaps 21 of the spacer expander 12 to limit the circumferential 
movement of the rail 11. 
The spacer/expander 12 is preferably of the type shown in U.S. Pat. No. 
2,789,872, incorporated herein by reference. The construction utilizing 
the protrusion 20 on rail 11 is also applicable to other spacer/expanders 
which have a radial recess into which the protrusion 20 can extend, for 
example, spacer/expanders such as shown in U.S. Pat. Nos. 3,814,444, 
4,579,351 and 4,585,237, incorporated herein by reference. 
The spacer/expander 12 preferably comprises a consecutive series of 
alternative inward and outward corrugations. The inner corrugations have 
inner crowns 22 and the outer crowns 23 which are connected by upper and 
lower connecting legs 24 separated by slots 26. Such slots paralleling the 
upper and lower edges of the spacer expander extend from the edges of the 
crowns 22 to and partly into the crowns 23. From each of the inner crowns 
22, a short pad 25 extends at both upper and lower edges. Such pads 25 
extend upwardly above and downwardly below the edges of the spacer 
expander respectively and are of narrow width. It is apparent that each 
connecting leg 24 and each part thereof above and below the slot 25 
therein has reversely curved and portions extending from a middle portion 
and that slots 26 reach from one curved end portion to the other, 
providing a readily controlled, uniform flexibility in the several 
connecting legs in circumferentially contracting the spacer/expander. 
Such structure is made from a single length of flat metal material. The 
connecting portions between the inner and outer crowns, because of their 
location and because of the removal of the metal when the slots are made, 
have flexibility so that they yield when the spacer expander member is 
contracted circumferentially. It is evident that such spacer expander 
member is readily made from flat ribbon stock of a desired thickness, the 
openings provided by the slots being easily made by punching metal from 
the strip stock, the pads being left upon cutting metal between successive 
pads at the side edges of the stock. 
With such spacer/expander 12, thin parted metal rails 11 are used, one at 
the upper and one at the lower side, the inner edges of which come against 
the outer sides of the pads 25. The corrugations extending outwardly from 
the crowns 22 lie between the upper and lower sides of the lower and upper 
rails 11 respectively, providing support therefor and holding them spaced. 
The rails at their outer edges extend beyond the spacer expander a short 
distance but such outwardly extending corrugations provide ample and 
stable support for the rails. In practice, it may be desirable to incline 
the pads 25 at an angle, which may be between 5.degree. and 25.degree., to 
the planes of the inner crowns 22 so that the inner edges of the rails 11 
pressing thereagainst will cause the inner portions of said rails to tend 
to move into a sealing engagement against the opposite sides of a ring 
groove in a piston in which the piston ring, consisting of the rails and 
the spacer/expander of my invention, is installed. The width of the pads 
25, that is, the distance they extend above and below the upper edges of 
the spacer/expander is such that the pads are readily received in the ring 
groove but do not reach to the opposite sides thereof. U.S. Pat. No. 
2,789,872 is incorporated herein by reference. 
The protrusion 20 is preferably made by a type of punching operation which 
is shown schematically in FIGS. 6-8. The rail 11 is positioned on a flat 
plate 30 which has a radial projection 31 that locates the rail by 
engaging the gap 13. A punch P is moved axially to form the protrusion 20 
by a punching operation. The axial extent of movement of the punch is 
controlled by a stop 32 in the form of a threaded screw that engages a 
member 33 that moves with the punch. 
As shown in FIGS. 5, 5A and 8, the protrusion 20 extends radially inwardly 
but lies entirely within the planes of the side surfaces 35, 36 of the 
rail 11. 
The position of the protrusion 20 is spaced radially from the outer 
diameter of the rail. 
When the rails are assembled on the expander 12, the protrusion 20 extends 
into one of the gap between adjacent pads of the spacer/expander and 
circumferentially locates the rail. Because the protrusion 20 lies 
entirely between the opposed surfaces of the rail, the rail 11 need not be 
positioned with the protrusion toward any particular surface, that is, the 
rail 11 can be positioned with a protrusion axially outwardly or axially 
inwardly with respect to the spacer/expander. 
The radial magnitude and circumferential location of the radial protrusion 
20 are constrained within limits to achieve successful results. The 
dimensional constraints are limited on the lower limit to that of 
obtaining sufficient magnitude to effectively stop rotation. A lower limit 
of approximately 0.001" has been verified. The upper limit is determined 
based on acceptable limits of distortion to the rail which may be 
tolerated. The punching of the rail to form the protrusion locally 
increases the radius of curvature at the location of the punching which 
could potentially negatively impact the sealing capability of the rail 
O.D. to the bore. Testing has shown that locating the feature near the 
rail gap (13) minimizes the impact of the distortion; and when combined 
with a maximum radial protrusion of 0.009", results in negligible 
distortion of the rail. 
Once the rails are assembled uncompressed to the spacer/expander, the 
protrusions lightly restrict the rotation. Due to the rounded shape of the 
protrusions, the rails can be readily rotated relative to the expander for 
final circumferential positioning (staggering). When the assembly is 
subsequently compressed to cylinder bore diameter, the tension induced 
contact forces between the expander contact pads and the rail I.D. greatly 
increases the locking characteristic of the protrusion. 
It can thus be seen that there has been provided which obviates the problem 
of increased oil consumption; which can be achieved at relatively low 
cost; which can be assembled readily without any possibility of 
misassembly; and which would be effective to eliminate any possibility of 
alignment of the gaps of the oil ring rails and the spacer expander.