Abstract: A device for automatically limiting the steplessly adjustable speed of a drive motor for the spindle of a grinding machine to a speed which is the maximum permissible motor speed for the grinding wheel currently being used has a motor-driven speed regulator which, upon a stopping of the spindle, returns automatically to an initial position corresponding to the lowest permissible motor speed and has exchangeable protective hoods associated with respective grinding wheel diameters and types which can be releasably secured on the grinding spindle housing. Each protective hood, with the exception of the protective hood for the grinding wheel with the lowest maximum permissible speed, has associated with it a receptacle with several contacts which, depending on the maximum permissible speed for the associated grinding wheel, has two contacts connected by an electrical bridge.

Abstract: A metering apparatus for liquids containing granular solids, in particular lapping liquid. The stream of liquid issuing from the feed pipe is conveyed with a wide area against a substantially vertical wall, to run down thereon in the form of a thin film of uniform thickness. The collecting pipe is arranged on the side of the wall which is remote from the liquid film. The wall has an orifice therethrough in its lower zone for the free end of the collecting pipe which extends obliquely upwardly. The collecting opening has a cross section which widens with progressive movement of the collecting pipe through the orifice.