Patent GB-1533111-A (GB)
Title: Underwater device
IPC: B63G8/42
Filed: 1970-01-27
Abstract: 1533111 Apparatus for buoys CANADA NATIONAL DEFENCE MINISTER OF 27 Jan 1970 3965/70, Heading B7A A water-expandable device for use as an underwater stabilizing or support means or platform comprises a flexible, soft-walled, water impermeable element and means for connecting the element to means for supplying water thereto in response to a condition sensing means to cause the element to form a semi-rigid structure of predetermined configuration. The device when packaged is capable of being dropped from an aircraft, the expansion only taking place after the package has hit the water and sunk to a desired depth. In one form (Fig. 4), the device has three arms 1, 2, and 3, e.g. of polyethylene, radiating in "star" form from a centre header 4. The header 4 contains a pump, communicating with the surrounding water and with the inside of each of the three arms through a one-way valve arrangement, and by a water immersible battery. The pump is actuated by condition sensitive means, e.g. a hydrostatic switch, a time delay switch or a signal responsive switch. The arms provide a platform for any suitable form of sensing means, e.g. geophones 5, 6, 7 mounted on the arms adjacent their ends. The header 4 is connected by means of a tether to a positively buoyant cannister floating on the water surface and containing telemetry means. Because the arms and header are slightly negatively buoyant, the expanded structure tends to be suspended at the required depth on the end of the tether. When collapsed to form a package, the arms 1, 2, 3 are coiled about the geophones 5, 6, 7 in a configuration which radiates from the header 4 as shown in Fig. 3. In an alternative form (Fig. 6, not shown), the inflatable arms form a "delta" configuration. In order to ensure uniform sequential uncoiling of the arms, an expansion control element such as a contact zipper may be secured longitudinally to each arm so that when the collapsed arm is coiled, an adhesive interface is effectively formed between adjacent loops of the coil. In the case of a platform to be deployed where strong currents are prevalent or if the structure is to be towed through water, the structure instead of being formed from arms is of a one-piece streamlined configuration, e.g. a triangular or circular disc (Figs. 7, 8 and 9, not shown). Further possible configurations are those of a toroid or semi-toroid (Figs. 10 and 11, not shown). The latter configuration may be used to support a fishnet. A further form of ship towable semirigid expanded structure is shown in Fig. 12, in which a tow cable 60 carries a water hose connected to a water pump on board ship and to the header 61 of the structure, the latter consisting of arms 62, 63. Water under pressure is continuously applied to the structure so as to maintain it-in its semi-rigid state, yet permitting sufficient quantities of pressurized water to be discharged through orifices 64 to assist in the propulsion of the structure. Bleed-off parts 65 control the boundary layer around the structure for drag reduction purposes. A third arm 66 (shown in phantom) may be provided between the trailing ends of arms 62, 63 and connected thereto by headers 68. A further use to which the invention may be put is the stabilizationof a buoy (Figs. 13 and 14, not shown) provided with a mechanically released impact plate which is released when the buoy strikes the water, enabling the water to reach a salt water battery which actuates a pump. Ambient water is pumped into the collapsed element and forces it downwardly through the bottom of the buoy to form a stabilizing member. Where a structure according to the invention is towed, the pump may be dispensed with and a shaped neck or funnel-like header provided for supplying water to the towed element by "ram effect".