Abstract: A normally helically interacting shaft and nut assembly having a common longitudinal axis along which the nut is normally displaced linearly by rotation of the shaft is provided with a wedging surface in a passage, located by or in the nut, inclined at an angle to the longitudinal axis and facing into an aperture in the nut normally partially occupied by a threaded portion of the shaft; and a detent, such as a ball, in the passage. In the event of failure of the normal engagement between nut and shaft (such as can occur with the threads on the nut wearing) free relative linear motion of the nut relative to the threaded shaft causes the wedging surface to displace the detent towards, and into engagement with, the threaded shaft and thereafter maintain the detent in such engagement so as to inhibit further free linear motion by the nut relative to the shaft. At least a part of the nut engaging with the shaft can be of a self lubricating material such as a graphite loaded plastics material.

Abstract: Corrosion and scale-inhibiting compositions which are useful in recirculating aqueous systems comprise a mixture of a phosphate compound, a phosphonate compound comprising 1-hydroxyethylidene-1,1-diphosphonic acid or nitrilotris(methylene)triphosphonic acid, an aryl triazole, and a salt of a metal selected from the group consisting of molybdenum, tungsten and chromium. In the preferred embodiment of the invention, the phosphate compound is present in a weight percent ratio in the range of from about 2.5:1 to about 4:1 weight percent per weight percent of the metal salt. An example of an effective anti-corrosion composition comprises a mixture of sodium tripolyphosphate, 1-hydroxyethylidene-1,1-diphosphonic acid, benzotriazole and sodium molybdate, said composition being present in an amount of from about 5 to about 5,000 ppm.

Abstract: An ocean floor surficial dredging apparatus is contemplated for retrieving particulate minerals from on and below the ocean floor. Such apparatus comprises first means for providing sufficient downward driving forces for enabling the first means to at least partially penetrate the ocean floor. The apparatus embodies second means operatively connected to the first means and actuable for providing sufficient positive buoyant force for extricating the first means from the seabed and returning it to the ocean surface. Also envisioned, such apparatus includes a third means operatively connected to the first means for permitting passage, therepast, of the particulate minerals whenever downwardly penetrating the seabed and for trapping particulate minerals of predetermined sizes in the first means, whenever, the first means is being extricated from the seabed in response to the actuations of the second means.