Devices for governing the speed of hydraulic press plungers

1,110,985. Measuring speed photo-electrically. SPETSIALNOE KONSTRUKTORSKOE BJURO "URALCHERMETAVTOMATIKA". Dec. 5, 1966, No. 54266/66. Heading G1A. [Also in Division G3] In a system for controlling the speed of a plunger 1 in a hydraulic press by comparison of its actual speed with a reference 5, the actual speed signal is produced by a device 3 comprising two discs of electrically conducting material, having optical gratings 14 at their periphery which overlap between a light-source 19 and photo-cell 20, and having magnets 10 for inducing damping eddy currents in at least one of the discs. The discs are rotated in the same direction by an endless wire 17 spring- loaded at 18, or by a weighted or sprung single wire. The magnets may be permanent but as shown they are electromagnets whose energization is weakened at higher speed ranges by a selector switch 11, and is cut off altogether by 12 during all but the working stroke of the press.