Abstract: A drawing apparatus is disclosed which has two wheels of equal diameter mounted coaxially on a frame. A writing implement is preferably mounted in a aperture at the midpoint of the line defined by the centers of the wheels. The wheels are driven by a pair of stepping motors which rotate in response to digital pulses. If the wheels are turned at the same rate in the same direction linear movement is accomplished. If the wheels are turned at the same rate in opposite directions, directional motion is accomplished.

Abstract: This invention relates to an apparatus for separating fine material from coarse material.The screens at present in use in the mining industry usually are so-called shaking screens. They comprise a screen-cloth, which is subjected to a vibration movement. This type of screen, however, has a very high noise level and also is exposed to heavy wear owing to the vibrations, to which the screen parts are subjected.The present invention has the object to provide an apparatus of the kind referred to above, in which the noise level and the mechanical wear are substantially lower than at conventional screens.