| 摘要 |
PCT No. PCT/AU95/00032 Sec. 371 Date Sep. 10, 1996 Sec. 102(e) Date Sep. 10, 1996 PCT Filed Jan. 23, 1995 PCT Pub. No. WO95/21032 PCT Pub. Date Aug. 10, 1995A sieve screen deck comprising having a frame and a sieve screen resiliently mounted to the frame so as to allow a limited amount of movement between the sieve screen and the frame. The sieve screen has flexible side walls. The screen deck also has a rapping mechanism which itself has a ram fixed at one end relative to the frame and acting at its other end on a drive shaft via a crank arm. The drive shaft extends across the sieve screen and is rotatably journalled in the respective side walls of the sieve screen. The rapping mechanism also has a rapping bar connected to the drive shaft by resilient elongate arms. The rams is actuated so as to move the rapping bar at intervals from a rest position wherein the rapping bar is spaced a short distance from the sieve screen and the sieve screen is supported by the frame to a primed position. In the latter portion, the rapping bar is spaced further away from the sieve screen and a predetermined distance above its rest position and the screen is raised relative to the frame and thereafter to release the mechanism to allow the rapping bar and the sieve screen to fall back to the rest position with such force that the rapping bar will cause the resilient arms to bend sufficiently to cause the rapping bar to strike the sieve screen.
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