Piston oil control ring

In a composite oil control ring for reciprocating piston internal combustion engines which includes a relatively soft parted cast iron ring and an expander-spring disposed internally of the ring to bias the same into sealing engagement with a cylinder wall, a parted annular insert rail of wear-resistant metal is disposed between the expander and the ring to reduce wear on the ring and to prevent embedment or unitization of the ring and spring. The insert rail is generally V-shaped in radial cross section to provide an enhanced bearing area for sliding between the insert and spring, and to reduce potential blockage by the spring of aligned oil drain ports in the insert and the ring.

The present invention relates to piston rings, and particularly to 
composite oil control rings of the type which includes a parted cast iron 
sealing ring and a ring-expanding spring. More specifically, the invention 
relates to improvements in the composite oil control ring disclosed in the 
U.S. application of Edward G. Carlson, Ser. No. 635,580 filed Nov. 28, 
1975. 
It is an object of the present invention to provide a composite oil control 
ring of the described type which is economical to manufacture and 
assemble, which provides increased bearing contact area for sliding 
contact between the spring and ring to reduce unit loading and increase 
operating life, and/or which provides improved oil drainage through the 
ring.

Referring to FIG. 1, a conventional piston 20 is disposed to reciprocate 
within a cylinder 22 of a gasoline- or diesel-powered internal combustion 
engine. Piston 20 is provided with the usual peripheral groove in which a 
composite oil control ring 24 in accordance with the invention is 
disposed. Referring to FIGS. 2-6 which show in greater detail a preferred 
embodiment of composite oil control ring 24, the composite ring comprises 
a conventional parted cast iron sealing ring 26 and a split annular coiled 
expander-spring 28 disposed internally of ring 26 within the associated 
piston groove, spring 28 being disposed in an opposing, radially inwardly 
facing spring-receiving groove or channel 30 in ring 26. Spring 28 is 
adapted to expand circumferentially, whereby ring 26 is expanded by spring 
28 in the circumferential direction into sealing engagement with the 
opposing wall of cylinder 22 (FIG. 1). The axially outer or sealing face 
of ring 26 has a pair of outwardly tapering frustoconical side portions 32 
and a central cylindrical portion 34 cut by an annular oil-collecting 
channel 36. A plurality of elongate oil drain vents or ports 38 are 
arrayed circumferentially about ring channel 36 and connect outer channel 
36 with inner ring channel 30. A composite oil ring of the type so far 
discussed is shown an discussed in greater detail in Hesling U.S. Pat. No. 
3,195,903. As generally taught by the above-referenced Carlson 
application, a parted annular insert rail 40 of wear-resistant or 
wear-coated metal is disposed between spring 28 and ring 26 to reduce wear 
on the ring and to prevent embedment or unitization of the ring and 
spring. 
In accordance with the present invention, insert 40 is generally V-shaped 
in radial cross section, as best seen in FIG. 3, and has a plurality of 
oil drain vents or ports 42 disposed in circumferential array about the 
outwardly directed apex 44 thereof. Spaced, inwardly diverging insert 
sides 45 form a concavity, as viewed in FIG. 3, into which spring 28 is 
received. Spring 28 is in sliding contact with each side 45 of insert 40 
and is spaced thereby from insert apex 44. The included angle between side 
portions 45 in the assembled condition of insert 40 is determined by such 
parameters as the axial and radial ring thicknesses, spring cross 
sectional diameter, etc. A preferred included angle of between 90.degree. 
and 135.degree. is presently envisioned. Preferably, drain ports 42 are 
generally aligned with ring drain ports 38, as best seen in FIGS. 2 and 5. 
In the preferred embodiment of the invention shown in FIGS. 1-6, apex 44 
of insert 40 is flattened, such that ports 42 are formed in a generally 
cylindrical portion of the insert rail. 
Insert rail 40 possesses several significant advantages over that disclosed 
in the above-referenced Carlson application. The V-shaped configuration of 
the insert makes the insert self-retaining in ring channel 30 in that the 
radial edges 46 of the insert become embedded in the opposing wall of ring 
channel 30, as best seen in FIG. 4, so as to resist forces tending to pull 
the insert out of the ring. Insert 40 may be attached to ring 26 at a 
subassembly stage to minimize the number of parts handled during final 
engine assembly. Since ring 26 and insert 40 are attached to each other, 
the gaps thereof must be aligned, as shown at 48 of FIG. 2, so that the 
ring/insert combination can expand circumferentially. Yet another 
important advantage of the invention is that two areas of sliding contact 
or bearing areas are provided between insert 40 and spring 28, as best 
seen in FIG. 3, to reduce unit loading between the insert and spring at 
each point of contact, and to thereby reduce wear and increase the 
operating life of the composite control ring. Moreover, the V-shaped 
configuration of the insert rail spaces spring 28 from insert apex 44, and 
thereby greatly reduces the potential for interference or blockage of 
aligned oil drain ports 38, 42 by the spring. 
An alternative embodiment of the invention is illustrated in FIG. 7 wherein 
the spring-receiving channel 50 of the ring 52 has a V-shaped channel root 
54, as contrasted with the flat or cylindrical root of channel 30 (FIG. 
3). An insert rail 56 is formed in a corresponding V-shape and has drain 
ports 58 located at the radially tapering apex thereof. Although the 
modification of FIG. 7 is depicted as having insert 56 attached to ring 52 
as is preferred, such modification possesses a potential advantage over 
the preferred embodiment (FIGS. 1-6) in that the insert may be made "free 
floating" in the ring groove, if desired, by reducing the radial dimension 
of the insert while retaining a substantial bearing area for sliding 
contact between the opposing angulated faces of the insert and ring. The 
embodiment of FIG. 7 is not presently preferred because ring groove 30 
(FIG. 3) is less expensive to manufacture, and because truncated apex 44 
(FIG. 3) improves venting and coiling characteristics of the insert. It 
will be recognized, of course, that insert 40 (FIGS. 1-6) may be used with 
ring 52 (FIG. 7) where desired and will possess all of the above-noted 
advantages of insert 56. 
A second alternative embodiment of the invention is illustrated in FIG. 8 
in which a layer 60 of resilient material, such as polyurethane or another 
synthetic elastomeric compound, is bonded around the radially inner face 
of each side portion 45a of insert rail 40a. Ring 26 and spring 28 are 
identical to those discussed hereinabove with reference to FIGS. 1-6. 
Material layers 60 not only prevent direct metal-to-metal contact between 
spring 26 and rail 40a, but also allow a small amount of resilient 
circumferential movement of the spring relative to the insert rail without 
sliding.