Underwater assemblies with flooded actuators and methods for using same

This application claims priority from U.S. Provisional Patent Application Ser. No. 61/019,668, filed Jan. 9, 2009, the disclosure of which is hereby incorporated herein by reference in its entirety.

This invention relates generally to underwater devices, and more specifically to underwater devices with movable members.

Many submersible vehicles are constructed with actuators mounted inside the pressure hull of the vehicle because they are otherwise easily damaged by water. These existing actuators typically have a mechanical linkage, the motion of which imparts a force or torque on an externally mounted control fin or similar member as means of steering or propulsion. Except in critical cases, where oil-backed seals are used, water is typically excluded by a dynamic seal providing a friction fit against the linkage. “Friction fit” is defined herein as a linkage-seal interaction wherein motion of the linkage with respect to the seal causes friction owing to forceful contact between them.

A friction fit can cause problems, including abrasion, lockup and energy loss. “Abrasion” is defined herein as loss of material from the seal or shaft, producing a change in friction fit. “Lockup” is defined herein as link immobility with respect to the hull. “Energy loss” is defined herein as the energy required to combat friction or viscous or viscoelastic dissipation in the seal. Abrasion can degrade a seal in a matter of hours, forcing removal of the vehicle from service for seal replacement. Abrasion rate is a function of seal preload, or tightness, and the resulting friction force on the linkage. Abrasion is also proportional to operating depth because water pressure deforms the seal, pushing more tightly against the linkage. Preloading and seal deformation due to water pressure also determine the depth at which friction exceeds actuator strength and lockup occurs.

Leaks and lockup together determine the practical depth range of a submersible vehicle using dynamic seals for actuators that penetrate the pressure hull. These depths are typically shallow relative to those at which a submersible vehicle might otherwise easily operate. At the same time, friction loss consumes energy and, thereby, shortens the duration of submersible vehicle operation. Clearly, a reliable and affordable actuator that can reduce or eliminate friction loss and permit a greater range of operating depth for submersible vehicles would be desirable.

As a first aspect, embodiments of the present invention are directed to an underwater assembly. The underwater assembly comprises: a hull having an internal cavity that is in fluid communication with the external environment; an inductive actuator mounted within the cavity of the hull; a current source mounted in the hull and electrically connected to the actuator; and a movable member connected with the actuator and positioned external of the hull. Provision of current to the actuator causes the movable member to move relative to the hull.

In some embodiments, the assembly is an underwater vehicle, and the movable member assists in propelling and/or navigating the vehicle. In additional embodiments, the assembly includes a controller that controls the magnitude of current provided to the actuator.

As a second aspect, embodiments of the present invention are directed to an underwater vehicle comprising: a hull having an internal cavity that is in fluid communication with the external environment; an inductive actuator mounted within the cavity of the hull; a current source mounted in the hull and electrically connected to the actuator; a movable member connected with the actuator and positioned external of the hull; and a propeller mounted to the hull and configured to propel the vehicle. Provision of current to the actuator causes the movable member to move relative to the hull.

As a third aspect, embodiments of the present invention are directed to a method of controlling the orientation of a movable member on an underwater assembly. As a first step, the method comprises (a) providing an underwater assembly, comprising: a hull having an internal cavity that is in fluid communication with the external environment; an inductive actuator mounted within the cavity of the hull; a current source mounted in the hull and electrically connected to the actuator; and a movable member connected with the actuator and positioned external of the hull. The method further comprises (b) receiving instructions at a controller, the instructions providing information associated with the position of a movable member. The method also comprises (c) generating current in the actuator with the current source, wherein the magnitude of the current generated is determined by the instructions received at the controller, the current generated in the actuator causing the movable member to take a predetermined position relative to the hull. In some embodiments, the assembly is an underwater vehicle.