Machine element or mechanism – Mechanical movements – Rotary to or from reciprocating or oscillating
Reexamination Certificate
1999-09-28
2001-07-24
Herrmann, Allan D. (Department: 3682)
Machine element or mechanism
Mechanical movements
Rotary to or from reciprocating or oscillating
C366S128000
Reexamination Certificate
active
06263750
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for producing directional vibrations.
2. Description of the Related Art
Devices of this kind are known and are used to introduce directional vibrations into a structure. The structure can be a vibrating table for compacting concrete or an implement, e.g. a vibrating plate for soil compaction. In the case of vibrating tables, the directional vibrations are predominantly produced by vibrators positively synchronized by electrical/electronic or mechanical means or by pendulum vibrators.
The vibrators are two centrifugal weights which rotate in opposite directions and the mutually opposed centrifugal-force components of which cancel each other out, while the force component plane in the drawn perpendicularly to that through the axes of rotation of the centrifugal weights add up to give a resultant force and effect the vibration. The centrifugal weights are synchronized in a mechanical, electrical or electronic manner, in some cases with considerable complexity. To avoid the occurrence of damaging forces in a direction transverse to the actual direction of vibration, considerable precision of synchronization is required.
In the case of soil compaction equipment, especially vibrating plates, as in the case of vibrating tables, it is known that a purely directional vibration can be obtained by rotating two centrifugal weights with the same m x r (where m x r is the product of the mass of the unbalance weight and the radius of the center of gravity) in opposite directions at the same speed about mutually parallel axes. For this purpose, the unbalance weights in the known equipment, are mounted in a common housing and are coupled positively to one another for rotation and are both driven in opposite directions at the desired identical speed by a common drive.
Particularly when using vibrating tables, the known way of producing directional vibrations has proven problematic because of the high degree of design complexity associated with it and the costs this entails.
A device of this kind is known from GB-A-2 103 333. The device described has, inter alia, inflatable chambers, the variable stiffness of which determines the intensity of the vibration produced by centrifugal weights on a bracket.
OBJECTS AND SUMMARY OF THE INVENTION
The object on which the invention is based is therefore to specify a device by means of which directional vibrations can be produced and fed into a structure while keeping the complexity of the design to an acceptable level.
According to the invention, the object is achieved by a device with the features of patent claim
1
. Advantageous developments of the invention can be taken from the dependent claims.
A device according to the invention for producing directional vibrations is distinguished by at least two centrifugal weights with essentially the same m x r which can be driven in rotation independently of one another in opposite directions at essentially the same speed about mutually parallel axes; a largely rigid carrier, on which the centrifugal weights, of which there are at least two, are rotatably mounted; and by a bracket on which the carrier can be mounted in such a way by means of a holder that the carrier can be moved relative to the bracket.
It has surprisingly been found that, when the drive for the centrifugal weights is switched on in the device designed in the manner described above, automatic synchronization of the two centrifugal weights takes place almost immediately if the carrier carrying the centrifugal weights has a certain freedom of motion 1) in a direction parallel to the common plane of the axes of rotation of the centrifugal weights, i.e. in a direction perpendicular to the direction of vibration and perpendicular to the axes of rotation of the centrifugal weights and 2) perpendicular to the common plane of the axes of rotation, i.e. in the direction of the vibrations to be produced. This freedom of motion is generally incorporated in the design by means of a certain elasticity of the material and, if required, can be adjusted to a suitable magnitude. However, it is a prerequisite for this that the carrier should be largely rigid. For this reason, the centrifugal weights of the unbalance-based vibration generator run as though they were coupled positively to one another to produce a purely directional vibration without this being in fact the case, thus avoiding the usual high design complexity in this respect and the associated proneness to faults. Furthermore, assembly is easier since the entire device can easily be disassembled into independent subcomponents. This is significant particularly when assembling vibrating tables.
For this reason, a particularly preferred embodiment of the invention is distinguished in that the carrier can be moved relative to the bracket in the direction of the directional vibration to be produced and in a direction perpendicular to the direction of vibration and perpendicular to the axes of rotation of the centrifugal weights.
The vibration to be produced is advantageously aligned perpendicular to a plane passing through the axes of rotation of the centrifugal weights.
In a particularly advantageous development of the invention, the holder has at least one spring element for transmitting the movement of the carrier in the direction of the directional vibration. The spring element can be a rubber-elastic element. In another advantageous development, the holder has at least one spring element for transmitting the movement of the carrier in a direction perpendicular to the direction of vibration and perpendicular to the axes of rotation of the centrifugal weights. The spring elements ensure mobility of the carrier in the holder and hence relative to the bracket without allowing impermissible play to occur between the carrier and the holder. The spring elements also provide effective noise reduction, especially when combined with damping elements, since the vibrations associated with structure-borne noise which are produced by the centrifugal weights and their drive are transmitted only partially to the bracket, if at all.
It is advantageous if the stiffness of the spring element or elements is matched to the stiffness of the carrier. This ensures that self-synchronization of the two centrifugal weights occurs irrespective of the structure to be excited.
A particularly advantageous embodiment of the invention is distinguished in that the holder has two holding units which are attached to the bracket and between which the carrier is accommodated in a movable manner. The holding units are situated opposite one another with the carrier in between them, allowing the carrier to be held reliably in position without the need for additional components.
It is advantageous if each of the holding units has a spring element into which the carrier is inserted.
In a preferred embodiment of the invention, a respective drive for each centrifugal weight is arranged on the carrier. Since, according to the invention, the centrifugal weights synchronize themselves automatically, it is not necessary to synchronize them additionally by mechanical, electrical or electronic components.
It can be particularly advantageous for the centrifugal weights to be divided in half axially with a drive motor arranged in between in each case in order to even out the bearing and shaft loads on the motors.
It is particularly advantageous if the bracket is part of a structure into which the directional vibrations can be introduced. This means that the holder or holding units are mounted directly on the structure to be excited or that the bracket can be attached to the structure as a structural unit together with the holder and the carrier.
It is likewise advantageous if the structure is a vibrating table or a vibrating plate because, when the device is used for such applications, the complex vibration generators previously known can be replaced with a more simple device.
REFERENCES:
patent: 2531706 (1950-11-01), Signeul et al.
patent: 3203264 (1965-08-01)
Breitenbach Johann
Bromberger Thomas
Kramp Edith
Mark Alexander
Maurer Thomas
Boyle Fredrickson Newholm Stein & Gratz S.C.
Herrmann Allan D.
Wacker-Werke GmbH & Co. KG
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