Device for ascertaining alignment errors in shafts arranged in tandem

Claim 1

Apparatus for ascertaining whether two shafts (3) and (4) arranged in tandem have their center lines aligned and the extent of any parallel and/or angular displacement thereof, said apparatus comprising: a signal emitter positioned on the first of the shafts to be aligned to emit a signal indicative of the position of the first shaft; a signal reflector positioned on the second of the shafts (4) to be aligned in the path of a signal from said emitter reflecting the signal received from said emitter back to the first shaft, said reflector comprising a rectangular reflecting prism system (6) arranged on the second shaft (4), with the plane of the prism hypotenuse (6a) of said prism system essentially perpendicular to the center line of the second shaft (4); and a signal receiver positioned on the first shaft (3) to receive the signal reflected by said reflector and producing an electrical signal determined by the position at which the signal from said reflector impinges on said receiver, said signal receiver comprising a measurement receiver (7), arranged on the first shaft (3) and generating two signals, which correspond to the coordinates (x,y) of the distance of the light-beam incidence point (A) from a fixed reference point (0) in a measurement plane essentially perpendicular to the center line of the first shaft (3), whereby one of said signals indicates parallel displacement of one shaft with respect to the other, and the other of said signals indicates angular displacement of one shaft with respect to the other.