Abstract: Portable electrically operable apparatus for monitoring and for giving warning of the presence of a predetermined environmental hazard in the neighbourhood of the apparatus and which comprises a portable housing, an electrical power source arranged in the housing, a first monitoring unit arranged in the housing and operable to detect the presence of a predetermined environmental hazard e.g. radiation or undesired gases, a second monitoring unit arranged in the housing to monitor the operation of the apparatus for fault detection, a warning indicator arrangement provided on the housing and operated by the first or the second monitoring unit so as to provide a warning indication upon the detection of a predetermined hazard or upon fault detection, and a safe-operation indicator arrangement provided on the housing and connected to the first and second monitoring units so as to provide a safe-operation indication in the absence of hazard detection or fault detection.

Abstract: Disclosed is a process and apparatus for induction hardening of the flank, root and tip surfaces of gear teeth so as to provide a surface-hardened layer along said surfaces. An electrically energizable inductor head carries out movement along the space between a pair of adjacent gear teeth, the inductor head having an external profile matching the profile of the space between the gear teeth. Guides maintain clearances between the inductor head and the tooth surfaces, during movement of the inductor head, the clearance being a minimum between the inductor head and the root surface and varying in predetermined manner along the flank surfaces to achieve heating along the flanks and root surfaces to a uniform predetermined temperature. Jets of coolant are directed to the surfaces of the unheated flanks, tips, heated flanks and root of the pair of gear teeth to achieve rapid cooling of said surfaces. The gear is immersed in mineral oil or other non-aqueous quenching agent.