EP0712702A2 - Apparatus for generating vibrations - Google Patents

Abstract

Each module (1) contains two parallel imbalance shafts (4) with rotary out-of-balance weights. On different modules imbalance shafts in tandem of identical rotary sense are interconnected by shafts. The modules contain supports (6) between the imbalance shafts and the vibrated material. The parallel imbalance shafts rotate in opposite directions. Pref. two modules have each one imbalance shaft, and are firmly coupled, via a holder, orthogonally to the imbalance shaft position. At least two adjacent modules may be coupled to parallel imbalance motors (2).

Description

The invention relates to a vibrating device with oscillating, spaced modules with two parallel, counter-rotating unbalance shafts with unbalances, the modules being arranged one behind the other in the longitudinal direction to the unbalanced shafts and adjacent modules being coupled via shafts attached to the successively arranged unbalanced shafts , - A vibrating device with oscillating, spaced modules with two parallel, counter-rotating unbalance shafts with unbalance, whereby on different modules, one behind the other unbalanced shafts of the same direction of rotation are coupled via shafts attached to the successively arranged unbalanced shafts, and - a vibrating device with vibrating, mechanically coupled modules and with parallel arranged, counter-rotating unbalance shafts with unbalance.

Such a vibrating device is known from DE-AS 25 47 762. The vibrating device has adjacent modules, each of which includes two parallel shafts with unbalance. The unbalanced shafts lying one behind the other in the longitudinal direction are coupled to one another by shafts. The modules each have a wall element to be shaken (arranged vertically). Each wall element is inserted by means of elastic seals in windows of a fixed shape, which is intended for filling concrete.

From the magazine "Betonwerk + Fertigteil-Technik", Issue 8, 1979, pages 478 to 485, a vibrating device with a continuous, rigid table surface and unbalanced shafts mounted under this table surface is known. Several unbalance points lie next to each other, two each are arranged one behind the other and coupled together. Two motors each drive the unbalanced shafts via a synchronization gear. Since the table surface is rigid and without subdivision, natural bending frequencies with fixed oscillation peaks and valleys occur during operation.

This does not guarantee a uniform mixing of the material to be shaken on the table surface, for example concrete. In addition, a large table surface generates considerable forces during operation, which require extensive measures to improve the rigidity and durability of the table surface. In such a case, the vibrating device has a considerable weight, which increases the energy consumption. Since the table surface is rigid, the parallel unbalanced shafts cannot synchronize themselves. The required synchronizing gears are therefore exposed to considerable stress. Subsequent enlargement of the table surface is only possible with extensive considerations to increase the rigidity of the entire table surface and to improve the resilience of the synchronization gears.

DE-A-3 112 198 discloses a vibrating device with an elongated shape, which is fastened to a plurality of support elements which are mounted so that they can vibrate, each with two modules. The modules each have an unbalanced shaft, the unbalanced shafts of the two modules of a support element being aligned in parallel. The two modules are attached to a common connecting element, which extends perpendicular to the position of the unbalanced shafts.

The invention has for its object to provide a large-area vibrator, which is composed of small and light modules, with no stability problems and a particularly good distribution of the material to be vibrated can be achieved.

• daß die Module oben Trägerelemente aufweisen, die zumischen den Unwuchtwellen und dem zu rüttelnden Gut angeordnet sind und daß die Trägerelemente der Module mit Befestigungsmitteln ausgerüstet sind, die gemeinsam ein Behältnis für als zu rüttelnde Gut halten, oder
• dadurch daß jedes Modul oben ein Trägerelement aufweist, daß mindestens zwei Module nebeneinander mit parallel zueinander angeordneten Unwuchtwellen derart gekoppelt sind, daß alle unmittelbar benachbarten, an vershiedenen Modulen angebrachten Unwuchtwellen sich gleichsinnig drehen und dabei die von den Unwuchten der Module hervorgerufenen Kräfte auf zueinander parallelen Wirkungslinien liegen, und daß die Unwuchtwellen Bestandteile von während des Betriebs eingeschalteten Unwuchtmotoren sind oder
• dadurch daß genau zwei Module mit jeweils einem länglich geformten Trägerelement und jeweils einer darunter befindlichen, in Längsrichtung des Trägerelementes ausgerichteten Unwuchtwelle vorhanden sind, daß jede Unwuchtwelle Bestandteil eines während des Betriebs eingeschalteten Unwuchtmotors ist, daß die Module senkrecht zur Längsrichtung der Trägerelemente, ungefähr in der Mitte der Trägerelemente über ein längliches Verbindungselement gekoppelt sind, daß das Verbindungselement die Trägerelemente bezüglich einer geraden Linie, die durch die Längsrichtung des Verbindungselements senkrecht zu den Unwuchtwellen verläuft, biegesteif und leicht drehelastisch verbindet und daß an den Enden der Trägerelemente Befestigungsmittel angebracht sind, die gemeinsam ein Behältnis für das zu rüttelnde Gut halten.

According to the invention, this object is achieved by

• that the modules have support elements at the top, which are arranged between the unbalanced shafts and the material to be shaken, and that the support elements of the modules are equipped with fastening means which together hold a container for the material to be shaken, or
• in that each module has a carrier element at the top, that at least two modules are coupled next to each other with unbalanced shafts arranged parallel to one another in such a way that all immediately adjacent unbalanced shafts attached to different modules rotate in the same direction and the forces caused by the unbalance of the modules on mutually parallel lines of action lie, and that the unbalanced shafts are components of unbalanced motors which are switched on during operation, or
• in that there are exactly two modules, each with an elongated support element and each with an imbalance shaft located underneath and aligned in the longitudinal direction of the support element, that each imbalance shaft is part of an unbalance motor that is switched on during operation, that the modules are perpendicular to the longitudinal direction of the support elements, approximately in the Center of the support elements are coupled via an elongated connecting element, that the connecting element connects the support elements with respect to a straight line, which runs through the longitudinal direction of the connecting element perpendicular to the unbalanced shafts, rigid and slightly torsionally elastic and that fastening means are attached to the ends of the support elements, which are common consider a container for the goods to be shaken.

The counter-rotating rotation of the unbalanced shafts arranged in parallel ensures a directional swinging movement - perpendicular to the surface formed by the unbalanced shafts.

With large-area vibrators, it is more economical to use several small unbalance motors or several small unbalanced shafts than one large unbalanced motor or an unbalanced shaft with a heavy unbalance; because the division into smaller modules results in lower forces, so that the vibrating device for stiffening measures requires less material and can therefore be carried out with a particularly low weight. It also makes it possible to keep the overall height of the vibrating device low. Finally, transportation is also made easier with a low weight and small overall height.

The unbalanced shafts can be components of unbalanced motors that are switched on during operation. It is also conceivable for the unbalanced shafts to be driven by a single motor or by a plurality of oscillating or stationary motors.
The container can be, for example, a shape, e.g. B. for a component made of concrete.
If several modules are arranged next to one another, the immediately adjacent unbalanced shafts attached to different modules can be brought into a rotational movement in the same direction by means of a belt or a toothed belt.

In the case of several modules connected one behind the other and several modules lying side by side, only a single belt or toothed belt is sufficient to move immediately adjacent unbalanced shafts attached to different modules in the same direction of rotation.

The shafts that connect unbalanced shafts arranged one behind the other can be cardan shafts or shafts that have a coupling on at least one end. The couplings on the shaft ends can compensate for an offset or deflection. For this purpose, the couplings should not be flexible in the direction of rotation, but they should be in the axial direction. In the event of an offset in the (unbalance) shafts arranged one behind the other or in the event of deflections, proper operation is possible.

In the embodiments of the vibrating device with more than two modules, a large-area vibrating table can be formed by designing the carrier elements as flat surfaces, which are all at the same height. Such a vibrating table can be expanded as required (subsequently) by coupling modules of the same design, without the need for a new dimensioning or reinforcement of the modules already installed.
The gaps between the surfaces of the carrier elements can be closed by elastic seals. It is also conceivable that adjacent surfaces overlap. These measures prevent smaller parts from falling through the interstices of the individual surfaces or getting caught between them.
With such a vibrating table (with a change without seals), a particularly uniform vibration distribution is ensured if the vibrating table serves as a vibrating base for a freely movable ("dancing") shape thereon; A viscous mass introduced into the mold is then compressed particularly evenly, because the compression effect is particularly effective at the frequencies and amplitudes that occur.
So that the shape does not fall laterally from the vibrating table, the vibrating table surface could be laterally surrounded by an edge.
It is possible to dimension the modules in such a way that they can only oscillate up to a load limit with regard to the loaded weight and are unyielding when the load limit is exceeded.

The load limit could then be set so that it is reached when an industrial truck drives onto the vibrating table surface. It is possible to support the individual modules of the vibrating table on air springs.

The connecting element, which runs perpendicular to the elongated support elements of the vibrating device with exactly two modules (each with a single unbalanced shaft) and is connected to the support elements, can be, for example, a double-T support that is always rigid along its longitudinal direction and is slightly torsionally flexible .
In this embodiment, it is ensured that a directional oscillating movement occurs perpendicular to the plane formed by the unbalanced shafts, at the same time unfavorable force distributions are avoided by the torsionally elastic design if the container mounted on the carrier elements is not torsionally rigid under torsional loads about the longitudinal axis.
In such a vibrating device with two modules and a connecting element, magnetic vibrators can also be used as drives for generating vibrations instead of the unbalance motors.

If the container with the goods to be shaken - for example a mold - is fastened to the carrier elements with fastening elements and is therefore not freely movable, the noise during operation is significantly reduced, which leads to considerable cost savings in production because of complex noise-reducing construction measures can be dispensed with. It is also advantageous that the operating personnel is exposed to lower levels of health hazards due to the noise reduction.

If the carrier elements of the modules have fastening elements, the container fastened there takes on the function of stiffening the entire vibrating device across all modules. In these cases, a stable design of the fastening elements is of particular importance. At the same time, it is advantageous in many cases if the fastening means are easily detachable so that the container can be replaced quickly.

In this sense, clamping devices are particularly cheap, especially when the container to be clamped has a shape, for example for Railway sleepers are made of concrete. Molds filled with concrete can then be quickly clamped onto the vibrating device one after the other to produce a larger number of railway sleepers.

If the hydraulically moved piston of a clamping device is inside the hydraulic cylinder with the container for the material to be vibrated clamped due to the maximum possible stroke of the piston within the hydraulic cylinder, there is a direct positive connection between the piston and the piston during the vibrating process - without any hydraulic oil in between Hydraulic cylinder ensured. This places a particularly low load on the hydraulic mechanism.

In the case of a tensioning device for a vibrating device, the tensioning element could have a hydraulic cylinder with a piston with an arm pointing outward in the longitudinal direction of the hydraulic cylinder, the length of the tensioning element being hydraulically variable by moving the arm.

The clamping member could be dimensioned so that it is in the container for the material to be shaken in the.

An exemplary embodiment of the invention is described in more detail below with reference to nine drawings, from which further details and advantages result.

Fig. 1

eine Rüttelvorrichtung mit einem fest eingespannten Rüttelelement;

Fig. 2

die Untersicht einer Rüttelvorrichtung nach Fig. 1;

Fig. 3

die Untersicht einer großflächigen Rüttelvorrichtung mit mehr als zwei parallelen Unwuchtwellen;

Fig. 4

eine Seitenansicht der Rüttelvorrichtung nach Fig. 3;

Fig. 5

die Untersicht einer Rüttelvorrichtung mit lediglich zwei Unwuchtmotoren;

Fig. 6

eine Spannvorrichtung;

Fig. 7

die Spannvorrichtung nach Fig. 6 mit Angabe der Bewegungsrichtung beim Lösen;

Fig. 8

die Spannvorrichtung nach Fig. 6 mit Angabe der Bewegungsrichtung beim Spannen;

Fig. 9

eine Abwandlung der Spannvorrichtung nach Fig. 6.

Show it:

Fig. 1

a vibrating device with a firmly clamped vibrating element;

Fig. 2

the bottom view of a vibrating device according to Fig. 1;

Fig. 3

the bottom view of a large-area vibrator with more than two parallel unbalanced shafts;

Fig. 4

a side view of the vibrator of FIG. 3;

Fig. 5

the bottom view of a vibrator with only two unbalance motors;

Fig. 6

a jig;

Fig. 7

the tensioning device of Figure 6 with indication of the direction of movement when loosening.

Fig. 8

the tensioning device according to Figure 6 with indication of the direction of movement during tensioning.

Fig. 9

a modification of the tensioning device according to FIG. 6.

1 shows a side view of a vibrating device with three modules 1. Each module 1 has two unbalance motors 2, the unbalanced shafts of which are aligned parallel to one another. The unbalanced shafts protrude with their two ends beyond the stand of the unbalance motors 2. At these ends of the unbalanced shafts there are unbalances which each rotate within a housing 5. As an example, the unbalance shaft with the unbalance at both ends of the left unbalance motor 2 is indicated by dashed lines. The aligned unbalanced shafts arranged one behind the other are coupled by shafts 7, which are connected to the unbalanced shafts via couplings 9. Elongated support elements 6 are mounted on the unbalance motors 2 and extend into the plane of the drawing. A tensioning device 11 is attached to both ends of the elongated support elements. The clamping devices 11 hold a mold 10 which has a high material rigidity.
The shape 10 runs through the entire vibrating device and gives it 6 stability by fastening to the carrier elements.
Any number of modules 1 can be arranged one behind the other; as an example, a third module 1 is drawn in dashed lines.

Fig. 2 shows the vibrating device according to Fig. 1 in the bottom view. Two parallel rows of unbalance motors 2 coupled one behind the other by shafts 7 can clearly be seen. The unbalance shafts of the unbalance motors 2 in the opposite rows rotate in opposite directions. Any number of additional modules 1 can be connected. Overall, however, the vibrating device should not be longer than the shape 10 to be clamped.

Fig. 3 shows a large-area vibrating device, which is composed of partial table surfaces I, II, ... XV. The vibrating device has a total of more than just two rows of unbalance motors M1 ... M16.
Each subtable surface I ... XV forms a module with two unbalance motors rotating in opposite directions. Imbalance motors M1 ... M16 arranged one behind the other in the longitudinal direction are connected to one another via couplings and shafts. On two adjacent subtable surfaces I ... WV rows of unbalance motors arranged side by side are positively synchronized via a toothed belt Z (or a chain). The toothed belt Z is attached to the associated toothed belt pulleys of the motors M14 and M15, M16 and M29 at the end of the rows with the unbalance motors M2, M6, M10, M14 and M3, M7, M11, M15 and M4, M8, M12, M16. The unbalance of the rows of unbalance motors M1 ... M16 connected by the toothed belt Z should always be aligned in the same direction during assembly, for example, all in an alignment downwards or to the right. In this way, the tensile stresses acting on the toothed belt Z are kept low.

Instead of the forced synchronization using a toothed belt Z, it is also possible to mount a gearbox in a fixed position, which is coupled to the parallel rows of unbalance motors M1 ... M16 via two shafts. Subtable surfaces I ... XV can be coupled in any number in the manner described.

FIG. 4 shows a side view of the vibrating device according to FIG. 3, specifically with a view of the toothed belt Z. The directions of rotation of the unbalance motors M1 ... M16 arranged in rows one behind the other can be seen. The unbalance motors, which are attached to a single module, run in opposite directions. The unbalance motors M14, M15 and M16, M29 connected by the toothed belts Z are fastened under adjacent subtable surfaces and rotate in the same direction.

A further embodiment of a vibrating device can be seen in the bottom view in FIG. 5. There are only two modules 1 ', each having a single unbalance motor 2. Each of the two unbalance motors 2 is fastened from below to an elongated support element 6 '. The unbalance motors 2 are arranged parallel to one another, specifically the motor shafts (with unbalances attached to them) lie parallel to the elongated support elements 6 '. The motor shafts with the unbalance rotate in opposite directions, so that a swinging movement occurs perpendicular to the plane of the drawing. The carrier elements 6 'are arranged at a distance from one another and connected in the middle by an elongated connecting element 12. The support elements 6 'each have a tensioning device 11 at their ends. All four clamping devices 11 together hold a shape 10 'that of the Clamping devices 11 is pressed from above against the carrier elements 6 '.

The connecting element 12 is designed to be rigid and torsionally elastic along its central axis, which runs centrally between the outer edges of the clamped vibrating element, ie it does not bend, but is easily rotatable about its central axis (torsion).
This enables a directional oscillating movement, even if the shape 10 'is not distinguished by a high level of material rigidity. In addition, the mold 10 'can be clamped well even if its underside has slight unevenness. The mold 10 'is held by clamping elements 11 which are attached to the ends of the two support elements 6'. The shape 10 'gives the vibrating device additional material rigidity.

Fig. 6 shows a clamping device 11 which works hydraulically. A clamping member 13 arranged perpendicularly - parallel to the side wall of the mold 10 '- has a hydraulic cylinder 14 in which a piston 15 can be moved up and down by the action of hydraulic oil flowing in or out. The piston 15 is connected to an arm 16 which projects out of the hydraulic cylinder 14 along the central axis thereof. This arm 16 transmits its upward and downward movement to a rotatably mounted lever 17 which is fastened to the arm 16 via a swivel joint 18. Laterally offset from the rotary joint 18, the lever 17 has a further joint 19, as a result of which the lever 17 is divided into two lever arms. The lever arm 20 facing away from the hydraulic cylinder presses on the mold 10 'from above when the tensioning member 13 has its maximum length.
Below the hydraulic cylinder 14, the tensioning member 13 has a further swivel joint 21, which moves a second lever 22. This lever 22 is movable about a pivot joint 23 which is laterally offset with respect to the tensioning element 13. The possible directions of rotation of all swivel joints 18, 19, 21 and 23 lie in the same plane. The lever arm 24 of the lever 22 facing away from the tensioning element 13 is supported at its end downward with a clamped shape 10 'on a projection 25 which is arranged below on the side of the lever arm 24 facing away from the carrier element 6' and at the same time is fastened below the carrier element 6 ' . A further swivel joint 26 is located between the swivel joint 23 of the lever 22 and the end of the lever 22 supported on the projection 25 available, on which - in the plane of the directions of rotation of all rotary joints 18, 19, 21, 23 and 26 - two angle pieces 27 are attached symmetrically left and right to the longitudinal direction of the lever arm 24, which on the sides facing away from the lever arm 24 parallel to the underside of the Carrier element 6 'create two levels, on each of which a coil spring 28 is supported. At its other end, the spiral springs 28 are fastened to the underside of the carrier element 6 'and, when the shape 10' is clamped in, press against the underside of the carrier element 6 '. When the tensioning member 13 is shortened by moving the piston 15 downward, the lever arm 20 moves upward about the swivel joint 19 away from the mold 10 '. The tensioning member 13 moves downward, whereby the lever 22 moves about the pivot joint 23 and pushes the lever arm 24 facing away from the tensioning member 13, so that its end moves away from the projection 25 upward. If the other clamping devices 11 are also open, the mold 10 'can then be easily removed from above.

In Fig. 7, the directions of movement of the parts of the clamping device 11 are indicated by arrows when loosening.

8 illustrates the directions of movement in the case of tensioning the tensioning device 11.
The parts shown in the latter two figures are explained in connection with the description of FIG. 6.

Fig. 9 shows a clamping device 11 ', which is slightly modified compared to that of FIGS. 6 to 8. The upper half of the figure corresponds to the representation in FIG. 6, this applies in particular to the hydraulically displaceable clamping member 13 and the mechanism with the upper lever 17, which, when the mold 10 ′ is clamped in, has its lever arm 20 on the mold 10 from above 'presses.
Parts of the same design are given the same reference numerals in FIGS. 6, 7, 8 and 9.
As in the embodiment in FIG. 6, there is a swivel 21 below the tensioning element 13, to which a lever 22 'is fastened. At its other end, the lever 22 'moves about a pivot joint 26'. 6, two angled holding elements 29 are attached symmetrically laterally to the left and right to the longitudinal direction of the lever 22 ', as in FIG. 6, each supporting a coil spring 28'; the coil springs 28 ' are each attached with their other end to the underside of the carrier element 6 '. Below the two spiral springs 28 ', two further spiral springs 30 are arranged below the angled holding elements 29, each of which is fastened with one end below the holding element 29 and with its other end on a shoulder 31 which is fixed relative to the carrier element 6'. All spiral springs 28 ' , 30 need not be prestressed when the mold 10 'is clamped.
When the clamping member 13 is shortened to take out the mold 10 ', the lever arm 20 rotates away from the mold 10'. The tensioning member 13 is pressed downward and with it the lever 22 ′ fastened at the bottom to the tensioning member 13 via the swivel joint 21. The movement of the lever 22 'is guided by an elongated guide element 32 which is connected to the lever 22' via a swivel joint 23 'which is laterally offset with respect to the tensioning element 13.
The guide element 32 slides when the lever 22 'is moved between two vertically arranged, parallel flanks 33 which ensure that the lever 22' at the level of the swivel joint 23 'can only move vertically upwards or downwards.

The above-mentioned springs 28 ′ and 30, which act on the end of the lever 22 ′ facing away from the tensioning element 13, together with the guide element 32 ensure that the lever is always in a horizontal position perpendicular to the axis of the tensioning element 13 and to the flanks 33 occupies.

Claims (10)

Vibrating device with oscillating, spaced modules (1) each with two parallel, counter-rotating unbalance shafts with unbalance, the modules (1) arranged one behind the other in the longitudinal direction to the unbalanced shafts and adjacent modules (1) via compliant to the one behind the other Unbalanced shafts (7) are coupled,
characterized,
that the modules (1) have support elements (6) at the top, which are arranged between the unbalanced shafts and the material to be shaken, and that the support elements (6) of the modules (1) are equipped with fastening means, which together form a container for the material to be shaken hold (Fig. 1, Fig. 2). Vibrating device with oscillating, spaced modules with two parallel, counter-rotating unbalance shafts with unbalances, whereby on different modules one behind the other unbalanced shafts of the same direction of rotation are coupled via shafts attached to the successive unbalanced shafts,
characterized,
that each module has a support element at the top, that at least two modules are coupled next to each other with unbalanced shafts arranged parallel to one another such that all immediately adjacent unbalanced shafts attached to different modules rotate in the same direction and the forces caused by the unbalance of the modules lie on mutually parallel lines of action , and that the unbalanced shafts are components of unbalanced motors (M1, M2 ... M16) which are switched on during operation (FIG. 3, FIG. 4). Belt device according to claim 2,
characterized,
that the support elements of the modules form flat table surfaces (I, II ... XV), which are all at the same height. Vibrating device according to claim 2 or 3,
characterized,
that immediately adjacent unbalanced shafts attached to different modules are synchronized via a fixed gear which is directly or indirectly coupled to these unbalanced shafts via shafts. Vibrating device according to one of the preceding claims,
characterized,
that the unbalanced shafts coupling shafts (7) are cardan shafts. Vibrating device according to claim 1,
characterized,
that the unbalanced shafts coupling shafts (7) have a coupling (9) at both ends. Vibrating device with oscillating, mechanically coupled modules and with parallel arranged, counter-rotating unbalance shafts with unbalance,
characterized,
that there are exactly two modules (1 '), each with an elongated support element (6') and an unbalance shaft located underneath and aligned in the longitudinal direction of the support element (6 '), that each unbalance shaft is part of an unbalance motor (2) switched on during operation is that the modules (1 ') are coupled perpendicular to the longitudinal direction of the carrier elements (6'), approximately in the middle of the carrier elements (6 ') via an elongated connecting element (12), that the connecting element (12) the carrier elements (6' ) with respect to a straight line, which runs through the longitudinal direction of the connecting element (12) perpendicular to the unbalanced shafts, connects in a flexurally rigid and slightly torsionally elastic manner and that fastening means are attached to the ends of the carrier elements (6 '), which together form a container for the material to be shaken hold (Fig. 5). Vibrating device according to one of the preceding claims,
characterized,
that at least one of the fastening elements, if present, is a tensioning device (11, 11 '), that this tensioning device (11, 11') has a lengthwise hydraulically changeable tensioning element (13), that when the tensioning element (13) is extended, a one end of the tensioning gear (13) rotatably fastened first lever (17) with a lever arm (20) facing away from the tensioning element (13) presses the container to be clamped for the material to be shaken onto the associated carrier element (6 ') and at the same time presses it against the other End of the tensioning element (13) rotatably attached second lever (22, 22 ') presses against the carrier element (6') in the direction of the first lever (20) via an elastic pressure element and that when the tensioning element (13) is shortened, the first lever (17 ) by rotating its lever arm (20) facing away from the tensioning element (13) away from the container in such a way that the container is exposed for removal. Vibrating element according to claim 8,
characterized,
that the pressure element is at least one spiral spring (28), which is supported at one end on an angle piece (27) fastened to the second lever (22) and, when the tensioning device (11) is closed, is pretensioned with its other end against the carrier element (6 ') presses that the second lever (22) is supported when the container is clamped at its end facing away from the spiral spring (28) on a projection (25) connected to the carrier element (6'), that when the tensioning member (13) is shortened the second lever (22) rotates about a swivel joint (23) arranged between spiral spring (28) and projection (25) and that the lever arm (24) of the lever (22) facing away from the tensioning element (13) moves upward from the projection (25 ) moved on (Fig. 6) Vibrating element according to claim 8,
characterized,
that the pressure element is formed by at least two springs (28 ', 30) arranged one above the other, one of which is inserted between a holding element (29) attached to the second lever (22') and the carrier element (6 ') and the other underneath between the holding element (29) and a shoulder (31) fixedly arranged with respect to the carrier element (6 ').

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