Hydraulic shock absorber

An aircraft assembly including a shock absorber, the shock absorber comprising:

• an inner housing portion slidably coupled to an outer housing portion to define a variable size chamber for containing shock absorber fluid, the region where the inner and outer housing portions overlap defining an annulus between adjacent surfaces of the inner and outer housing portions which varies in size in accordance with the extension state of the shock absorber;
• and
• a seal located within the annulus and arranged in contact with one of the inner and outer housing portions for confining shock absorber fluid to the chamber;
• wherein the shock absorber fluid comprises an electro-rheological or magneto-rheological liquid and the shock absorber includes a device for generating a magnetic or electric control field in the region of the seal in order to increase the viscosity of the shock absorber fluid such that the fluid in the region of the seal changes from a liquid state to a gel-like or solid state to inhibit passage of the shock absorber fluid beyond the seal;
• and
• wherein the control field is stronger in a region of the electro-rheological or magneto-rheological liquid relatively near the seal than in a region of the electro-rheological or magneto-rheological liquid relatively far from the seal.

A hydraulic shock absorber comprising:

• an inner housing portion slidably coupled to an outer housing portion to define a variable size chamber for containing shock absorber fluid, the region where the inner and outer housing portions overlap defining an annulus between adjacent surfaces of the inner and outer housing portions which varies in size in accordance with the extension state of the shock absorber;
• and
• a seal located within the annulus and arranged in contact with one of the inner and outer housing portions for confining shock absorber fluid to the chamber;
• wherein the shock absorber fluid comprises an electro-rheological or magneto-rheological liquid and the shock absorber includes a device for generating a magnetic or electric control field in the region of the seal in order to increase the viscosity of the shock absorber fluid such that the fluid in the region of the seal changes from a liquid state to a gel-like or solid state to inhibit passage of the shock absorber fluid beyond the seal;
• and
• wherein the damping characteristics of the shock absorber are substantially unaffected by a change in the strength of control field.

A hydraulic shock absorber comprising:

• an inner housing portion slidably coupled to an outer housing portion to define a variable size chamber for containing shock absorber fluid, the region where the inner and outer housing portions overlap defining an annulus between adjacent surfaces of the inner and outer housing portions which varies in size in accordance with the extension state of the shock absorber;
• and
• a seal located within the annulus and arranged in contact with one of the inner and outer housing portions for confining shock absorber fluid to the chamber;
• wherein the shock absorber fluid comprises an electro-rheological or magneto-rheological liquid and the shock absorber includes a device for generating a magnetic or electric control field in the region of the seal in order to increase the viscosity of the shock absorber fluid such that the fluid in the region of the seal changes from a liquid state to a gel-like or solid state to inhibit passage of the shock absorber fluid beyond the seal;
• and
• wherein the electro-rheological or magneto-rheological liquid in a damping region of the shock absorber is substantially unaffected by the control field.