Ballistic tolerant hydraulic control actuator and method of fabricating same

A hydraulic actuator comprising:

• (A) a movable member positioned within a housing and cooperating therewith to define at least one pressure chamber to receive hydraulic fluid to actuate the movable member within the housing,
• (B) wherein said housing comprises:
• (1) an outer wall of selected thickness t to satisfy actuator fatigue requirements,
• (2) a central sleeve snugly sleeved into said outer wall and being of selected structural characteristics so that shock waves generated in said outer wall due to projectile impact and penetration are imparted to said central sleeve with sufficient intensity to locally disintegrate and clear said sleeve, and so that thickness of the central sleeve is at least equal to the depth of petals formed in the outer wall by a threat projectile of diameter D impacting, penetrating, and passing therethrough, and which threat projectile forms a ratio t/D nearer to 1/3 than any other threat projectile,
• (C) means to actuate said movable member within said housing following the occurance of such projectile damage,
• (D) means to provide a wear resistant and protective layer to the central sleeve inner surface without preventing actuation of said movable member within said housing following the occurance of such projectile damage.

A hydraulic actuator comprising:

• (A) a movable member positioned within a hybrid housing and cooperating therewith to define at least one pressure chamber to receive hydraulic fluid to actuate the movable member within the housing,
• (B) wherein said hybrid housing comprises:
• (1) an outer steel wall of selected thickness t to satisfy actuator fatigue requirements,
• (2) a central sleeve of bonded graphite laminates snugly sleeved into and bonded to said outer wall and being of selected structural characteristics so that stress waves generated in said outer wall due to projectile impact and penetration are imparted to said central sleeve with sufficient intensity to locally disintegrate and clear said sleeve, and so that the thickness of the central sleeve is at least equal to the depth of petals formed in the outer wall by a projectile, and wherein the wall thickness of the central sleeve is greater than the maximum petal depth formed in the outer wall by projectile impact and penetration of the threat projectile having a diameter D which forms a ratio t/D with outer wall thickness t closer to 1/3 than any other threat projectile,
• (3) an inner wall of electroformed nickel sleeved into and bonded to the central sleeve so as to be cleared with the central sleeve and so that ballistically induced stress waves reflected therefrom also serve to clear the inner wall and central sleeve and weaken any petals left in the inner wall.

The method of producing a ballistically tolerant hydraulic servo cylinder capable of having a projectile of diameter D pass therethrough so that the nature of the ballistic damage caused thereby will permit continued movement of the servo movable member within the cylinder, comprising the steps of:

• (A) fabricating from a material having low residual stress a wear resistant inner wall of wall thickness about 0.030 inches or less and of a selected inner diameter required to permit the servo to perform its required function,
• (B) producing an outer wall of selected wall thickness t which will carry the necessary loads without fatigue failure to permit the servo to perform its required function, and made of selected material so that the impacting, penetrating, and passing therethrough of a projectile of diameter D will set up stress waves therein to be transmitted therethrough and so that petals will be formed therein of selected maximum petal depth no greater than the petal depth experienced from the threat projectile producing the ratio t/D closest to 1/3, and
• (C) producing a central sleeve member of material having low tensile strength in a radially inward direction so as to clear when subjected to stress waves imparted thereto from the outer housing and reflected therethrough from the inner wall, and having a wall thickness of at least the outer wall maximum petal depth, and
• (D) sleeving the central sleeve between the inner and outer walls in snug fit relationship so that the central sleeve is in radial compression and bonding it to each wall.