Patent ID: 8212431
Filing Date: 2012-07-03
Classification: H01H,H03K

Abstract:
1. A safety switching apparatus for failsafe shut-down of an automatically operated installation in response to a first signal and a second signal from a two-channel signaling device, with the first and the second signals each having a defined polarity, the safety switching apparatus comprising: a first terminal for supplying the first signal and a second terminal for supplying the second signal, a first and a second switching element, which together produce a redundant output switching signal for shutting-down the installation, a first circuit connecting said first terminal and said first switching element for supplying said first signal to said first switching element, and a second circuit connecting said second terminal and said second switching element for supplying said second signal to said second switching element, wherein said second circuit includes a first current path comprising a first pair of diodes from a bridge rectifier, a second current path comprising a second pair of diodes from said bridge rectifier and at least one further active switching element, and further wherein the at least one further active switching element selectively routes the second signal to said second switching element either via the first current path or via the second current path, depending upon the polarity of said second signal, such that said first and second switching elements produce said redundant output switching signal whenever current flows simultaneously through said first switching element via said first circuit and through said second switching element via either of said first and second current paths in said second circuit.