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A spherical spring mounting, for use by a handicapped person in a standing frame, comprises a central hub with a partly spherical outer surface, around which there are truncated spherical shells with intervening elastomeric layers. The hub may be connected with a selected shell so that a given degree of resilience can be provided.•GEW In order to combat flutter in fan blades of turbofan engines, Helmholtz resonators are built into the fan's duct wall near the region swept by the blade tips. These resonators consist of axial tubular cavities communicating with the duct through small openings in the duct wall.--EEU 4,352,487 43.40.Tm VISCOUS SPRING DAMPER Emile M. $htarkman, assignor to Gould, Incorporated 5 October 1982 (Class 267/35); filed 18 November 1980 This viscous spring damper has supports 16,18 connected by an elastomerit shear spring 20. Fluid flows between chambers 26, 34 through orifice 56 60 52 54 4; •o 12 "/•' 42 78 80 84 86 42 when the assembly is deformed. Elastomeric bladders 50, 80 have rings 70 and ribs 78 to minimize abrasion and prevent hydraulic lock.--GEW

problem that arises when the camera is self-focusing with an ultrasonic echo range finder intended to work in air. In this case, the original ultrasonic transducer is covered with a sound-absorbing cup in which two small transducers are included, one to receive the camera's transmitted signal, and the other to introduce a simulated echo. They are connected to a supplementary sonar system that is designed to work in water. The signal generated by the camera initiates a suitable pulse of underwater sound at a higher frequency to achieve the same narrow acoustic beam that would have been in air. The underwater echo is fed to a computer which determines the longer echo time that would have occurred in air, corrects that time for the difference in optical properties of air and water, and delivers the simulated echo at the proper time for the camera to focus on the object.--LB 1663