| 摘要 |
A vibratory drive for concrete block moulding machines has a drive shaft (2) which can be driven by a drive motor (25) and has an internal unbalance mass (3) and, mounted on said drive shaft (2), a cylindrical rotation body (5) with an external unbalance mass (6) and two stops (10 and 11). The drive shaft (2) is mounted, outside the rotational body (5), on a base plate or vibration plate (15). With full drive of the drive shaft (2), the internal unbalance mass (3) assumes a position determined by the first stop, in which it doubles the effect of the external unbalance mass (6). When the drive is switched off, the internal unbalance mass (3) assumes a position bearing against the second stop, in which the resultant unbalance is compensated to zero. To effect a very rapid start-up of the vibratory drive after switching off, the invention provides a control circuit (35) in the electrical circuit of the drive motor (25), which controls said drive motor (25) just such that the rotational speed of the drive shaft (2), and thus of the vibratory drive (1) does not decrease to below 80% of the nominal rotational speed in the operating position. The rotational speed is regulated slowly and smoothly back up to the nominal rotational speed such that the internal unbalance mass (3) does not leave the compensation position with respect to the outer unbalance mass (6). In the rest position, the vibratory drive can also be prevented from falling to below 80% of the nominal rotational speed by driving the external rotational body (5) by means of a further rotational motor. <IMAGE>
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