Claims
- 1. A piston and piston ring for a hydraulic or pneumatic mechanism especially for a dashpot, comprising a piston with a shock absorber is mounted on a piston rod; a cylinder separated into two chambers by said piston, said piston having at least two halves meeting a contact surface extending across an axis of symmetry; a plastic ring having an axial extent and a wall thickness, said axial extent being several times said wall thickness, said plastic ring resting in a groove extending around both halves; said groove having walls with elevations extending toward the groove, each elevation having an opposite, a distance between each elevation and said opposite being less than said axial extent of said ring.
- 2. A piston as defined in claim 1, wherein said elevations are wedge-shaped and extend radially.
- 3. A piston as defined in claim 1, wherein said elevations are trapezoidal in cross-section and extend radially.
- 4. A piston as defined in claim 1, wherein said ring has a first volume displaced by said elevations and said groove has a second volume not occupied between said elevations by said ring, said axial extent of said ring being dimensioned to ensure that said volume of the ring displaced by said elevations is less than said volume of said groove not occupied between said elevations by the ring.
Priority Claims (1)
Number |
Date |
Country |
Kind |
198 45 610 |
Oct 1998 |
DE |
|
BACKGROUND OF THE INVENTION
The present invention concerns a piston and piston ring for a hydraulic or pneumatic mechanism and especially for a dashpot.
That friction between the piston and cylinder can be decreased by mounting a preferably plastic ring around the outer surface of the piston is known.
DE 3 701 757 A1 discloses such a piston and ring. The ring is accommodated in a groove that extends around the outer surface of the piston. The ring that characterizes this particular prior art is very thin-walled and is accordingly also referred to as “sheet”. There are drawbacks to this system due to the need to maintain precise tolerances between the dimensions of the groove, the diameter of the cylinder, and the thickness of the sheet. These tolerances must allow the piston to travel in and out of the cylinder smoothly and can lead to displacement of the ring within the groove. The resulting rumbling noise can be heard inside the vehicle.
Tensioning the ring inside the groove axially or radially is known from DE9017933U1. The tensioning means, however, are very complicated and accordingly expensive.
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/SG98/00024 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO00/22316 |
4/20/2000 |
WO |
A |
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
244292 |
Perkins |
Jul 1881 |
A |
4955284 |
Faulkner |
Sep 1990 |
A |