Tool driving or impacting – Processes
Patent
1997-06-18
1999-06-15
Smith, Scott A.
Tool driving or impacting
Processes
173 49, B06B 118, B06B 116
Patent
active
059112808
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device and a method for compensating transverse vibrations on unbalanced-mass vibrators having a predetermined vibration direction. In the generic type of vibrator concerned here, the resultant exciting force F.sub.E determining the vibration direction is generated by two synchronously and oppositely rotating groups of part unbalanced-mass bodies, in the simplest instance each group having only a single part unbalanced-mass body.
A further feature of the type of vibrator with which the invention is concerned is that each group has at least one own drive motor, and that the two groups, but at least two part unbalanced-mass bodies belonging in each case to another group, are not or at least not constantly synchronized positively with one another via mechanical drive means, in order to maintain a specific rotary angle position. In the simplest version, a vibrator of this type consists of two part unbalanced-mass bodies which rotate oppositely and synchronously about two axes arranged parallel to one another and each of which is driven by its own motor.
Such vibrators are used for various purposes, synchronism occurring, in a simplest instance, as a result of self-called "self-synchronization" which can easily be achieved under the following conditions: the dynamic mass m.sub.dyn, which is to be set in vibration by the resultant acceleration or by the resultant unbalance force, must be capable of vibrating in an unimpeded manner (for example, being supported by springs), and a straight line drawn through the mass centre in the vibration direction must be the mid-perpendicular to a line which extends in the plane of the rotating unbalance centres from one axis of rotation to the other.
Vibrators of this type are also used for pile driving. In this case, the fact that positive synchronization between the two groups of part unbalanced-mass bodies by mechanical drive means can be dispensed with is considered to be a particular benefit in operational terms, for example on account of the contribution to noise reduction. Since the invention can be used to particular advantage here, it is described below with regard to pile-driving vibrators.
It may be noted at this juncture, as a reminder, that, in the case of pile-driving vibrators, the dynamic mass m.sub.dyn, which is set in vibration and which also includes the mass of the driven material, is always connected to a particular carrier appliance (for example, a leader or crane) via special vibration-insulating devices, such as, for example, spring yokes. The entire weight of the dynamic mass is introduced into the carrier appliance via this special vibration-insulating device. In pulling work, the weight to be transmitted also has the pulling force additionally superposed on it.
In the design of pile-driving vibrators of the type in question, care is taken to ensure that the dynamic mass m.sub.dyn to be set in vibration in the direction of the longitudinal axis of the driven material is distributed symmetrically, in such a way that the centre of gravity of the dynamic mass is located on a bisecting line which runs through the area centre of gravity of the profile area of the driven material, the said profile area occurring when a section is taken perpendicularly to the longitudinal axis.
Despite complying with this rule, vibration path components transverse to the intended vibration direction may occur on the dynamic mass to such an extent that it is no longer possible to work properly with the vibrator.
Transverse vibrations of this type may, on the one hand, originate from the incorrect orientation of the resultant exciting force F.sub.E of the part unbalanced-mass bodies themselves. The resultant exciting force is coupled kinetically to the dynamic mass and may therefore be influenced, too, by external disturbance forces, for example also as a function of the disturbance in the vibratory movement of the dynamic mass.
On the other hand, however, transverse vibrations may also be excited directly by disturbance forces acting on the dynamic
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patent: 5281775 (1994-01-01), Gremillion
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Gedib Ingenieurburo Und Innovationsberatung GmbH
Smith Scott A.
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