US Patent 7108099 Personal safety methods and apparatus

A safety anchor (20) for securing a user to a substantially vertical safety structure, e.g., elevator cable (21). Safety anchor (20) includes a back plate (26) to which are pivotally mounted a roller (28), inner cam assembly (30) and outer cam assembly (32). Each cam assembly (30,32) includes a lever arm (50,36) to which is mounted a cam (52,42). A user (25) is secured by means of carabiners and a short tether cable, for example, to the free ends of lever arms (50,36). Cable (21) threads between cams (52,42) which are pivoted to compress the cable in response to downward force exerted against the lever arms (50, 36).