Hydraulic actuator 202 (e.g. for aircraft landing gear) having an extension chamber 206 and a retraction chamber 208, and a bypass line 222 connecting and short circuiting the two chambers, the bypass line having flow restrictor 224 and a bypass valve 226 (e.g. in series). The valve has two valve actuating mechanisms of dissimilar and different types, one may be manually operated, the other may be a shape-changing material (e.g. phase change material, shape-memory material) which opens the valve when the temperature decreases below threshold (fig 6b). Flow restrictor may have 4 to 14 mm2 cross-sectional area. A valve status sensor may sense valve position or hydraulic fluid parameter in the bypass line. The bypass line may be external to the hydraulic ram connecting to the hydraulic lines 216, 218, within the wall of the hydraulic ram housing, or within the moveable piston 204.
Hydraulic actuator
2025-06-18
Patent
Electronic Resource
English
HYDRAULIC ACTUATOR AND MULTI-CYLINDER HYDRAULIC ACTUATOR SYSTEM
European Patent Office | 2019
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