Brakes – Internal-resistance motion retarder – Having a thrust member with a variable volume chamber
Patent
1993-08-30
1995-06-13
Oberleitner, Robert J.
Brakes
Internal-resistance motion retarder
Having a thrust member with a variable volume chamber
188275, 188279, 188316, 18832214, F16F 946, F16F 950
Patent
active
054234026
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a twin-pipe shock absorber comprising an oil reservoir between a working cylinder and an external pipe, a piston movable in a working cylinder, a hollow piston rod extending to the upper side of the working cylinder, a bottom plate closing the working cylinder, a disc inside the working cylinder between the piston and the bottom plate, said disc having a passageway and a non-return valve for control of upflow through said passageway, a central pipe extending through the piston into the hollow piston rod and the space above the piston, a damper valve assembly and regulating means to regulate the flow resistance excerted by the damper valve assembly depending at least on the relative movement of the piston and the working cylinder.
The main advantage of such a shock absorber is that the shock absorption can be adapted very rapidly to the frequency of movement of the unsprung wheel guide part which results in a considerable improvement of the driving comfort.
A twin-pipe shock absorber as mentioned in the preamble is disclosed in U.S. Pat. No. 4,682,675. The damper valve assembly of this known construction is a part of the piston and comprises a set of passageways occluded at one end by a first spring loaded flapper and a set of passageways occluded at one end by a second spring loaded flapper valve. The compression and rebound rates of the shock absorber are determined by the diameters of the passageways and the spring load on the flapper valves. The regulating means comprises a solenoid valve which is activated in case of a severe bump. By the activation of the solenoid valve the pressure differential across the piston is increased. As a result the stiffness of the shock absorber in compression is reduced. During the rebound or when the wheel falls into a hole the fluid pressure in the upper working chamber above the piston is increased and when the solenoid valve is actuated the upper working chamber is vented to the reservoir. This known construction is based on the idea to make the damper partially ineffective by influencing the pressure differential across the piston by a parallel leak. The main disadvantage thereof is that the damping characteristics are highly dependent on the velocity of the piston. An other disadvantage of the shock absorber disclosed in U.S. Pat. No. 4,682,675 is that the damper valve assembly comprises at least two valves each for one flow direction.
The object of the invention is to eliminate these disadvantages and to provide a shock absorber of the type mentioned in the preamble, in which the shock absorption is substantially independent of the piston velocity and of which the flow through the damper is in one direction only.
According to the invention the above twin-pipe shock absorber is characterized in that the piston has a passageway and a non-return valve for control of upflow through said passageway with a negligible damping capacity, that the damper valve assembly is a single uni-directional damper valve which is disposed at the bottom end of the central pipe, that the valve body of the damper valve is disposed on or forms part of an amplifier element, that the seat of the damper valve is on the lower side of the disc, that said amplifier element is displaceable up and down and has a narrow oil passageway, and that the regulating means are able to regulate the oil pressure below the amplifier element.
It is of essential importance that the oil flow on the ingoing and outgoing stroke of the piston is conveyed through the central pipe to one single damper valve, and that damping of this valve can be set rapidly. The piston of the shock absorber and the guide of the piston are simple in design: there is only one non-return valve which can be placed around the central pipe in such a way that it seals dynamically.
In order to produce the regulation by mechanical means, provision is made below the amplifier element for a mass inertia piston between two springs or spring systems, in which piston there is a passage which is provided with an non-return v
REFERENCES:
patent: 2512269 (1950-06-01), Ezbelent
patent: 3414092 (1968-12-01), Speckhart
patent: 3763970 (1973-10-01), Anderson
patent: 4838394 (1989-06-01), Lemme et al.
Koni B.V.
Oberleitner Robert J.
Poon Peter M.
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