Seal for a joint or juncture – Seal between relatively movable parts – Piston ring or piston ring expander or seat therefor
Reexamination Certificate
1999-05-07
2001-02-13
Melius, Terry Lee (Department: 3628)
Seal for a joint or juncture
Seal between relatively movable parts
Piston ring or piston ring expander or seat therefor
C310S311000
Reexamination Certificate
active
06186512
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to pistons in an internal combustion engine and more particularly to a piston ring for a piston.
2. Description of the Related Art
DE 195 01 792 C2 describes a piston with a piston ring being designed especially for the specific conditions of a flat piston. For this purpose, the piston ring has a width which is greater than a circumferential surface of the piston, so that there is an axially projecting length, which is shaped into a spring end, and which is supported on a top side of the piston.
All the embodiments of DE 195 01 792 C2 have a circular-arc-shaped transition which is greater than 180°. One embodiment, shown in
FIG. 3
, has a bent-over spring end which comes to bear with its face on the top side of the piston. Some disadvantages are associated with this under unfavorable conditions. Thus, in the case of a piston ring subjected to high loading, the bent-over spring end may turn in further in the direction of the inside of the piston ring, which can result in the piston ring loading itself. Furthermore, leakages may occur on the inside of the piston ring, and these leakages, although not serious, can be measured in a damping-force chart.
Particular loads always occur at a piston ring when the piston ring is used with a piston for a piston-cylinder unit having grooves in the cylinder. The piston ring is deformed in the direction of the groove root and may possibly be squeezed at the runout of the groove. The piston disclosed in DE 36 11 288 A1 therefore has a guide ring for the radial guidance of the piston and a piston ring, and which performs the sealing function. In this complicated solution too, however, the limits of loading in modern vehicles is reached.
SUMMARY OF THE INVENTION
An object of the present invention is to realize a piston ring for a piston which removes the problems known from the prior art with regard to strength and tightness.
This and other objects are achieved according to a first embodiment of the invention in that one spring end has a circular-arc-shaped transition, which is designed to be between 90° and 180°, and this spring end comes to bear on a first top side of the piston. The other spring end having an annular bearing surface, comes to bear in the region of the opposite second top side of the piston. The other spring end, with regard to the shaping angle, is adapted to the angle between the circumferential surface and the second top side in this region. This configuration of the piston ring not only enables the spring end on the piston ring to be shaped, but also enables the piston ring to be pushed onto the piston and then fixed by the forming of the annular bearing surface. In this case, a sufficiently large axial prestress can be obtained. The orientation of the shaped ends prevents contact with the inner wall of the piston ring.
In a further advantageous embodiment, the spring end on the first top side has sections which are designed with a larger shaping angle than their adjacent sections. In order to prevent the differences in stress between the differently shaped sections from becoming too large, provision is made for the sections, with different shaping angles, to form a corrugated course of the first spring end in the peripheral direction. Thus, the sections having a smaller shaping angle support the sections having a larger shaping angle, in which case incisions between the sections which would ordinarily be subjected to a notch effect, may be dispensed with.
To increase the maximum transverse-force loading, a pressure ring is arranged between the circumferential surface of the piston and the piston ring. This pressure ring prestresses the piston ring radially against the wall to be sealed. The object is not to increase the compressive prestress of the piston ring against the wall to be sealed, but to keep the sealing force constant and if need be achieve radial compensation in the event of transverse forces.
In another embodiment, the circumferential surface has a step, on which the pressure ring is arranged. The piston may be manufactured by means of a non-cutting production process.
Alternatively, the pressure ring of the piston ring may be arranged at the level of the transverse offset in order to increase the sealing effect of the transverse offset, provided the piston ring has a joint gap with a transverse offset.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
REFERENCES:
patent: 3645174 (1972-02-01), Prasse
patent: 5655634 (1997-08-01), Grundei et al.
patent: 36 11 288 A1 (1987-10-01), None
patent: 44 11 006 A1 (1994-12-01), None
patent: 44 10 996 C1 (1995-06-01), None
patent: 195 01 792 C2 (1997-06-01), None
Deppert Norbert
Wieser Robert
Wolki Peter
Cohen & Pontani, Lieberman & Pavane
Conley Frederick
Mannesmann Sachs AG
Melius Terry Lee
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