FIELD OF THE INVENTION

[0001] The present disclosure relates to hydraulic shock absorbers and dampers which can be adapted for use in a suspension system such as the systems used for transportation vehicles. More particularly, the present disclosure relates to a frequency dependent shock absorber, to provide different damping characteristics when subjected to input of differing

frequencies.

BACKGROUND OF THE INVENTION AND PRIOR ART

[0002] Frequency dependent valves such as those described in

WO03040586, WO2015130544, WO2015030884, typically contain a pressure chamber, whose change in volume is related to change in preload force on a valve assembly which throttles a fluid stream. Typically, movement which results in increase in preload force of the valve assembly is mostly opposed by reaction force from the valve assembly itself, but this sometimes results in sharp changes in pressure drop during a damper's stroke which is undesirable.

SUMMARY OF THE INVENTION

[0003] The present invention solves all the problems mentioned above as per the claims annexed to the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The accompanying drawings comprise:

[0005] Figure 1 shows a diagram illustrating the functioning of a valve according to the present invention.

[0006] Figure 2 shows a diagram illustrating a functional alternative with respect to the one depicted in figure 1 , with some additional optional elements.

[0007] Figure 3 shows a first embodiment of the current invention

[0008] Figure 4 shows a second embodiment of the current invention [0009] Figure 5 shows a third embodiment of the current invention [0010] Figure 6 shows a fourth embodiment of the current invention

DESCRIPTION OF REFERENCE NUMERALS

1 : Frequency dependent valve

10: Piston

11 : Flow channel

30: Piston rod

100: Valve assembly

150: Fluid flow

300: Pressure chamber

301 : Chamber wall

370: Spring element

380: Flow restrictor

390: Check valve

DETAILED DESCRIPTION OF THE DRAWINGS

[0011] The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the disclosure, its applications, or uses. Whenever the same reference number occur on different drawings, the same reference number designates similar or corresponding parts throughout the different drawings.

[0012] Figure 1 shows a diagram illustrating the functioning of a valve according to the present invention:

A valve (1 ) compring:

a pressure chamber (300);

a valve assembly (100) controlling a passage of fluid (150), the valve assembly (100) being configured in such a way that its preload force is controlled by the pressure chamber (300);

a spring element (370) that helps the valve assembly (100) oppose change in volume of the pressure chamber (300), its preload force also controlled by the pressure chamber (300); characterized in that:

for a given change in volume of the pressure chamber (300), reaction force from the spring element (370) changes faster than reaction force of the valve assembly (100).

[0013] When the pressure chamber (300) expands, the chamber wall (301) deforms and/or moves towards the main valve assembly (100). As a result the main valve assembly (100) receives a preloading force from the pressure chamber (300), at the same time the main valve assembly (100) imparts a reaction force of the same magnitude to the pressure chamber (300), opposing its expansion.

[0014] It is advantageous, for an improved frequency dependency performance, to have a spring element (370), which can be tuned, to help return the pressure chamber (300) back to its resting volume more quickly than would be in the case without the helping element (370). The helping element (370) imparts an additional force opposing the change in volume of the pressure chamber (300), which does so without adding to the preload force on the valve assembly (100).

[0015] Figure 2 shows a diagram illustrating a functional alternative with respect to the one depicted in figure 1 , with some additional optional elements. Flow restrictor (380) slows down fluid flow into the pressure chamber (300) and check valve (390) allows fast fluid exit out of the pressure chamber (300).

[0016] Structural representations of embodiments corresponding to the diagram of Figure 2 are shown in Figures 3-4:

A valve (1) compring:

a pressure chamber (300);

a valve assembly (100) controlling a passage of fluid (150), the valve assembly (100) being configured in such a way that its preload force is controlled by the pressure chamber (300);

a spring element (370) that helps the valve assembly (100) oppose change in volume of the pressure chamber (300), its preload force also controlled by the pressure chamber (300);

characterized in that:

for a given change in volume of the pressure chamber (300), reaction force from the spring element (370) changes faster than reaction force of the valve assembly (100).

[0017] Furthermore, in Figures 3 and 4:

said pressure chamber (300) comprises a moveable and / or deformable chamber wall (301),

said spring element (370) is configured to oppose movement or deformation of said chamber wall (301) which results in increased preload of said valve assembly (100);

said spring element (370) is higher in stiffness than said valve assembly (100).

[0018] Figure 3 shows an embodiment of the invention applied to a valve described in WO2015030884. In this valve (1), movement of chamber wall (301) towards the valve assembly (100) reduced volume of the pressure chamber (300) and preloads the valve assembly (100), so that the valve assembly throttles fluid flow (150) more. The spring element (370) helps the valve assembly (100) oppose change in volume of the pressure chamber

(300) .

[0019] Figure 4 shows an embodiment of the invention applied to a valve described in WO03040586. In this valve (1), movement of chamber wall

(301) towards the valve assembly (100) increases volume of the pressure chamber (300) and preloads the valve assembly (100), so that the valve assembly throttles fluid flow (150) more. The spring element (370) helps the valve assembly (100) oppose change in volume of the pressure chamber (300).

[0020] Figure 5 shows an embodiment of the invention applied to a valve described in BE2016/0014. In this valve (1), the piston (10) is able to slide on the piston rod (30). The valve assembly (100) is however fixed in its centre relative to the piston rod (30). Movement of the piston (10) relative to the piston rod (30) thus changes preload on the valve assembly (100), so that the valve assembly throttles fluid flow (150) more. The movement of the piston (10) is controlled by the pressure chamber (300) so that change in volume of the pressure chamber (300) results in changed preload of the valve assembly (100). The spring element (370) helps the valve assembly (100) oppose change in volume of the pressure chamber (300), and therefore movement of the piston (10).

[0021] Figure 6 shows an embodiment of the invention applied to a valve described in BE2016/0013. In this valve (1), movement of chamber wall (301) towards the valve assembly (100) increases volume of the pressure chamber (300) and preloads the valve assembly (100), so that the valve assembly throttles fluid flow (150) more. The spring element (370) helps the valve assembly (100) oppose change in volume of the pressure chamber (300). The spring element (370) is in this case the chamber wall itself (301), configured so that for a given change in volume of the pressure chamber (300), reaction force from the spring element (370) changes faster than reaction force of the valve assembly (100).

[0022] While the present invention has been described with reference to the embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made as defined in the following claims.