# US 2009/0260934 A1 · Shock absorber having resilient device in rebound chamber > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2009/0260934 A1 - Document ID: US20090260934A1 - Status: Published application - Kind: A1 - Application number: 12/442,266 - Filed: 2007-09-21 - Published: 2009-10-22 - Earliest claimed: 2006-09-21 - Assignees: Ohlins Racing AB - Inventors: Magnus Danek; Henrik Schiolde - Web page: https://patentgrep.com/patent/US20090260934A1 ## CPC - F16F 9/065: {Expansion chamber provided on the upper or lower end of a damper, separately there from or laterally on the damper} - F16F 9/064: {Units characterised by the location or shape of the expansion chamber (F16F9/068, F16F9/08 take precedence)} - F16F: SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION ## Abstract A shock absorber comprises a damping cylinder pressurized by a system pressure and divided by a piston into a compression chamber and a return chamber. A resilient device is disposed in the return chamber. The resilient device comprises a pressurizing member or pressurizing medium disposed in an inner volume that is delimited from the return chamber. The resilient device acts upon the damping medium volume in the return chamber such that the pressure initially during a compression stroke does not fall below a predetermined minimum pressure. As long as the pressure in the return chamber is less than the pressure created by the resilient device, the device is able to absorb energy. When the pressure in the return chamber is greater than the pressure created by the resilient device, the device becomes inflexible. The resilient device compensates for pressure reduction in the return chamber that occurs under rapid damping movements and that can cause cavitation during a compression stroke. ## Claims ### Claim 1 A method for controlling the pressure balance between two working chambers filled with damping medium and pressurized by a system pressure of a shock absorber, in which the shock absorber comprises a cylindrical body filled with a damping medium in the form of an oil and is divided by a main piston into a compression chamber and a return chamber in which a variable first damping medium pressure prevails in the compression chamber and a variable second damping medium pressure prevails in the return chamber, the second damping medium pressure in the return chamber being greater than a preselected minimum pressure by virtue of the fact that in or connected to the return chamber a resilient device in the form of an accumulator is provided, in which energy is stored through a build-up of pressure in a volume delimited against the return chamber in the resilient device and in which the stored energy is used to create a resilient function which gives rise to an increased pressure in the return chamber initially during the compression stroke. ### Claim 2 (depends on 1) The method as claimed in claim 1, wherein once a certain predetermined pressure ratio between the second damping medium pressure in the return chamber and the preselected minimum pressure prevails in the shock absorber, the effect of the resilient device is terminated by its bottoming against a mechanical stop. ### Claim 3 (depends on 1) The method as claimed in claim 1, wherein the pressure is built up in the resilient device by a compressed mechanical elastic member acting upon a pressurizing zone disposed inside the resilient device. ### Claim 4 (depends on 1) The method as claimed in claim 1, wherein the pressure is built up in the resilient device by a compressible medium introduced into the volume delimited against the return chamber and being pressurized to a predetermined fourth pressure. ### Claim 5 (depends on 4) The method as claimed in claim 4, wherein the predetermined fourth pressure generally coincides with the preselected minimum pressure. ### Claim 6 (depends on 1) The method as claimed in claim 1, characterized in that the preselected minimum pressure is lower than or equal to the system pressure with which the shock absorber is pressurized. ### Claim 7 A shock absorber intended for a vehicle, the shock absorber comprising a damping chamber adapted to be filled by a damping medium, the damping chamber adapted to be pressurized with a system pressure and the damping chamber being defined by a damping cylinder, the damping cylinder being divided by a main piston fastened to a piston rod, the main piston dividing the damping cylinder into a compression chamber and a rebound chamber, a variable first damping medium pressure adapted to act in the compression chamber, a variable second damping medium pressure adapted to act in the rebound chamber, a resilient device disposed directly adjacent to the return chamber, the resilient device comprising at least one of a pressurizing member and a pressurizing medium disposed in an inner volume enclosed from the return chamber and defined by the resilient device. ### Claim 8 (depends on 7) The shock absorber as claimed in claim 7, wherein a mechanical stop limits compression of the resilient device once compression by a certain predetermined distance has taken place. ### Claim 9 (depends on 7) The shock absorber as claimed in claim 7, wherein an energy-absorbing mechanical elastic member is positioned within the resilient device. ### Claim 10 (depends on 7) The shock absorber as claimed in claim 7, wherein the inner volume of the resilient device is adapted to be filled with an energy-absorbing, pressurizing compressible medium such that, when filled, that a certain pressure prevails within the volume. ### Claim 11 (depends on 7) The shock absorber as claimed in claim 7, wherein the resilient device is fixed to the piston rod closely adjacent to the main piston. ### Claim 12 (depends on 7) The shock absorber as claimed in claim 7, wherein the resilient device is mounted in the return chamber adjacent to an end of the damping cylinder through which the piston rod extends. ### Claim 13 (depends on 7) The shock absorber as claimed in claim 7, wherein the resilient device comprises at least one member that moves axially within the shock absorber. ### Claim 14 (depends on 7) The shock absorber as claimed in claim 7, wherein the resilient device comprises a first sprint part and a second spring part, at least one of the first and second spring parts being moveable relative to the other of the first and second spring parts, the mutually movable first and second spring parts being mutually sealed and the first spring part being arranged to move within the second spring part. ### Claim 15 (depends on 7) The shock absorber as claimed in claim 7, wherein the resilient device consists of comprises a piston disposed in and at least partially defining a piston rod volume inside the piston rod, in the piston rod volume is being connected to the return chamber. ### Claim 16 (depends on 7) The shock absorber as claimed in claim 7, wherein a spring characteristic of the resilient device is adjustable from the outside of the damping cylinder. ### Claim 17 (depends on 16) The shock absorber as claimed in claim 16, wherein the adjustable spring characteristic is created by a pretensioning of the mechanical member by adjustment of movable parts in relation to one another. ### Claim 18 (depends on 16) The shock absorber as claimed in claim 16, wherein the adjustable spring characteristic is created by replenishment or draining of pressurizing medium in the inner volume of the resilient device.