Freely vibrating screening machine

摘要

The invention relates to a freely vibrating screening machine which has a screen frame that is horizontal to inclined and has a drive which causes the screen frame to vibrate. Such vibration frequently proceeds horizontally in a to and fro displacement. It can also proceed upwardly or downwardly inclined, or else elliptically. A disadvantage of such screening machines consists in that screening material frequently stops up the screen openings, so that the screening performance is reduced and there is also damage to the screen openings. The invention eliminates this disadvantage by arranging for the screen frame to be additionally delayed in the vicinity of the upper reversal of direction of its vibrating movements through the action of an additional force on the screen frame. As a result, the particles jammed in the screen openings are largely flung out upwards, thus freeing the screen.