Designers of deep submersibles are reluctant to use conventional shafts and seals to penetrate the hulls of deep submersible, pressure vessels fearing seal failure under extreme pressures. The unique design of this patented system, designated LAMIFLEX®, incorporates elastomeric bearings in order to achieve an absolute hermetic seal and permit leak-free transfer of rotary motion up to at least 15 degrees through the hull of these highly pressurized vessels. External functions, such as control surface deflection, can be driven internally with inherent safety and backup. There are no sliding surfaces (packings, lip, or face seals) that could fail. It also exhibits a smooth spring-like reaction and limited shaft movement without friction. The new designs have been implemented and tested at pressures of 10,000 psi for more than a million cycles at ±15 degrees with no leakage.

Elastomeric Bearings achieve an absolute hermetic seal and permit leak-free transfer of rotary motion up to at least 15 degrees through the hull of these highly pressurized vessels.

Originated by Randolph Research for helicopter use in place of ball or roller bearings, these elastomeric bearings have long been used to support rotor blades against tons of centrifugal thrust while their pitch angles are oscillated hundreds of times per minute without any need for lubrication. Ease and smoothness of movement in that highload situation permit some helicopters to avoid using hydraulic boost on their control sticks.

The diagram depicts a sectional view of a hull penetrated by a vertical shaft. A LAMIFLEX bearing-seal surrounds the shaft. Its load faces are seated and sealed by static O-rings, located between a cylindrical receptacle in the hull and a flanged part of the shaft. The bearingseal is composed of many thin washerlike laminations of metal, which are alternated with rubber layers. All of the layers are bonded together to form a unified stack.

The large arrows on top represent hydrostatic fluid pressure (multiple tons per square inch) pushing down on the shaft and its flange and thereby pressing the bearing-seal against the hull receptacle. Simultaneously, the annular opening surrounding the periphery of the bearing-seal is also pressurized. Because of the unitary bonded construction of the bearingseal an absolute hermetic seal is achieved, i.e., there is no path for lateral fluid flow from the periphery toward the aperture. The thickness of rubber and metal layers (black and white, respectively) are greatly exaggerated for clarity. Typically, the layers (one hundred or more) are only a few mils thick. The thinness of the rubber layers prevents their being squeezed out under the high load. Torsional motions between any two metal washers result from parallel shearing action in the rubber layers between them, adding up to large angles of movement between the loading faces of the bearing-seals, with an opposing spring torque resulting from the rubber shear stress.

To provide a doubled barrier, a second, tandem bearing-seal can be builtin as an independent seal between a taller cylindrical wall and the top of the shaft flange. For even further backup, a normally unpressurized conventional O-ring can be placed in series and below the bearing-seal(s) as shown.

This work was done by William Hinks for Randolph Research Company, 2449 Kensington Road, Akron, Ohio 44333. The author may be contacted at whinks@randolphresearch. com or (330) 666-1667. More information is available on-line at US Patent No. 6,524,007.

Motion Control Tech Briefs Magazine

This article first appeared in the December, 2003 issue of Motion Control Tech Briefs Magazine.

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