Importance

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Abstract

A vibratory screening apparatus has two vibrator motors (19, 20, 19', 20') having respective out-of-balance weights arranged to produce substantially linear vibratory movement when, in use, these motors (19, 20, 19', 20') are running in mutually opposite directions, an electrical control means (37) connected to the motors (19, 20, 19', 20') and is selectively operable between a non-running mode in which both motors (19, 20) (19', 20') are stopped and two running modes in one of which both vibrator motors (19, 20, 19,' 20') run in mutually opposite directions to produce substantially linear vibratory movement and in the other of which at least one of the motors (19, 20, 19', 20') is rotationally reversed and both motors (19, 20, 19', 20') run to produce orbital vibratory movement. In a preferred arrangement, the out-of-balance weights (39, 42) in at least one (20) of the vibrator motors (19, 20) are adapted so that in one of the running modes the respective out-of-balance forces are mutually substantially equal, and in the other of the running modes the out-of-balance forces are mutually unequal. Alternatively, there is provided coupling means (47, 48), (49) for imposing rotational synchronization of the vibrator motors (19', 20') as required.

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First Claim