Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Reexamination Certificate
1998-11-30
2001-03-13
Bryant, David P. (Department: 3726)
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
C029S888075, C029S527600, C451S051000, C427S367000, C427S404000, C427S331000
Reexamination Certificate
active
06199274
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of making oil scraper (oil control) piston rings which have at least one circumferential web portion whose outer circumferential surface lies against and slides along the cylinder wall. To the outer circumferential web surface a wear-resistant layer is applied and is subsequently ground to form sharp edges on the web.
Oil scraper piston rings in a reciprocating piston-type machine serve for distributing an oil film over the cylinder wall. The oil film is just sufficient for lubricating the slide path of the upper piston rings (compression piston rings), and the oil scraper rings deliver the remainder of the oil back into the crankcase. It is an essential requirement that an oil scraper piston ring maintain, independently from the shape of the cylinder, a circumferentially constant surface pressure between the cylinder wall and the runner face of the ring.
Oil scraper piston rings which have an axially narrow circumferential web engaging the cylinder wall are exposed to high surface pressures during operation. For this reason the runner faces of such rings are conventionally provided with a wear-resistant layer, as disclosed, for example, in published European Patent Application 507 636. The piston ring has axially extremely narrow webs so that the surface pressure on the piston ring is very high. Since the wear-resistant layer conventionally constituted by a chromized outer layer of the web does not have the properties required for use in more current engine designs, a hardening of the webs has been effected by nitriding.
Dependent, for example, upon engine type, mode of operation and kind of oil, the oil scraper piston rings may have a service life of 400,000 km in automotive vehicles. Based on the desideratum, particularly in diesel engines, to reach a service life of 1,000,000 km and beyond, wear-resistant layers for compression piston rings have been developed as disclosed, for example, in published European Application 217 126. The wear-resistant layer has, throughout the entire layer volume, firmly embedded ceramic particles which lend the layer an extremely high load bearing capacity and wear resistance. Applying such a layer to conventional oil scraper piston rings has heretofore not been possible because the oil scraper piston rings, after applying a wear-resistant layer to the circumferential web surface, have to be ground in order to obtain a sharp edge which is indispensable for a good oil scraping operation. Since the grinding of the layer has led to the break-off of the ceramic particles, such a layer, although-known by itself, could heretofore not be used for oil scraping piston rings.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved method for applying a wear-resistant layer, known by itself, to oil scraper piston rings to thus extend their service life.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the method of making an oil scraper piston ring includes the following steps:
providing a base ring body including a circumferential web having flanks and an outer circumferential surface;
galvanically depositing on the web a wear resistant hard chromium layer having solid particles embedded therein;
applying a break-off resistant cover layer to the hard chromium layer; and grinding the cover layer to provide the outer circumferential surface of the web with sharp bounding edges.
The method according to the invention prevents a break-off of the solid particles during the grinding process. Dependent upon the particular use, various materials may be utilized for the cover layer. If, for example, a galvanized hard chromium layer without ceramic particles is used as the cover layer, such cover layer need not be entirely removed by the grinding operation. The residual hard chromium cover layer remaining on the oil scraper piston ring then works as a wear-resistant layer. If, after a certain service life, the hard chromium cover layer is worn off, the underlying second, improved hard chromium layer having the embedded solid particles becomes active. Such a manufacturing method further increases the service life of the oil scraper piston ring.
REFERENCES:
patent: Re. 33767 (1991-12-01), Christini et al.
patent: 2380654 (1945-07-01), Lane et al.
patent: 2696038 (1954-12-01), Hunt
patent: 2905512 (1959-09-01), Anderson
patent: 3671047 (1972-06-01), Umezawa
patent: 3729790 (1973-05-01), Sugahara
patent: 4057661 (1977-11-01), Züst
patent: 5461776 (1995-10-01), Wood
patent: 5721056 (1998-02-01), Wessling
patent: 5743012 (1998-04-01), Adams et al.
patent: 5779818 (1998-07-01), Wessling
patent: 2 050 441 (1972-08-01), None
patent: 17 51 573 (1978-01-01), None
patent: 196 21 721 (1996-12-01), None
patent: 0 217 126 (1987-04-01), None
patent: 0 507 636 (1992-10-01), None
Bryant David P.
Butler Marc W.
Federal-Mogul Burscheid GmbH
Kelemen Gabor J.
Venable
LandOfFree
Method of making oil scraper piston rings does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of making oil scraper piston rings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of making oil scraper piston rings will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2435725