Safety monitor for machinery

摘要

There is described a safety monitor for machinery comprising a pressure sensitive monitor switch mountable in the vicinity of the machinery and having first and second switching contacts which are normally separated but are arranged to be brought together in response to pressure upon the monitor switch indicative of a potential emergency, and at least one solid state switching device having first and second device inputs and at least one device output, the solid state switching device being controlled by voltage across the device inputs, which are connected across supply terminals connectable to a power supply, the first and second switching contacts of the monitor switch being respectively connected to the device inputs so that while the monitor switch is open circuit a voltage from the power supply is applied to the solid state switching device to maintain it in a first state indicative of normal operation whereas application of pressure to the monitor switch brings the switching contacts together providing a reduced resistance path across the device inputs and so reducing the voltage across them, thereby causing the output of the solid state switching device to change to a second state indicative of a potential emergency, the monitor switch and the solid state switching device being integrated in a single unit having outputs connectable to a control for initiating emergency action in response to the solid state switching device's second output state.