HK1082458B - Vibration exciter for soil compacting devices - Google Patents

Description

Vibrator for use in soil compactor

Technical Field

The invention relates to a vibrator for use in a soil compactor.

Background

Such vibrators are mostly preferred for use in vibrating tamper plates, and are known, for example, from EP0358744B 1.

A similar vibrator is described in DE10038206a 1. It has two congruent (formschlussig) coupled imbalance shafts (Unwuchhtville) which rotate relative to one another and each of which carries a fixed imbalance mass and a movable imbalance mass which rotates together with the imbalance mass relative to the fixed imbalance mass. The position of the movable unbalanced mass can be actively changed over a large area by the adjusting device.

When the imbalance shaft rotates, a resultant force is formed by the combined action of the different imbalance masses, which resultant force can be directed in the forward direction or in the backward direction as desired. The change of the direction of movement can be achieved by controlling the adjusting device of the movable unbalanced mass. When the user wishes to place the rammer in a stable condition, the resultant force of the centrifugal weights is placed in a vertical direction. This means that: the aim of tamping the ground can be achieved in a stable state of the machine.

However, the user does not always wish to carry out such a powerful tamping at a locally defined position on the ground. In particular, when the vibrating plate moves back and forth, an excessive and thus disadvantageous compacting of the ground surface is achieved at the so-called return or reversal point, since the force acting on the ground surface is at its maximum at this point, whereas in the forward or backward movement of the vibrating plate and the resultant force vector connected thereto, which is deflected forward or backward by 45 °, the force decreases to 1/√ 2 of the maximum value.

Although the above-described structures have thus proved to be excellent also in the tamping of soils, sandy soils or pebbles, they can show problems in the tamping of areas of bitumen or combined stones, since the greatest vertical forces prevailing at the reversal point can lead to punctiform settlement which can no longer be corrected. Thus, when rolling asphalt pavement, the vibration is typically turned off in reverse operation to avoid rolling too deep into the asphalt when the direction of travel returns.

To solve this problem, DE19943391a1 describes a vibrator in which the phase of the centrifugal weights can be adjusted by: the vertical components of the centrifugal force generated by the centrifugal weights cancel each other out in each rotational position, while the horizontal components of the centrifugal force add up correspondingly corrected. This results in the vibrating plate no longer having vertical vibrations penetrating into the ground in the steady state, but instead the shear stresses are introduced into the ground via a ground contact plate, with which cracks and gaps can be advantageously tamped in the surface of the asphalt.

This structure has also proved excellent in practice. However, the strong horizontal vibrations that prevail during stable operation of the vibrating plate are sometimes uncomfortable for the operator and it is not always desirable to tamp the ground surface.

DE1095752 describes an unbalanced vibrator for a soil compactor having two vertical unbalanced shafts parallel to one another, which each carry a fixed unbalanced mass and an unbalanced mass that is movable rotatably relative thereto. In the rest state of the vibrator, the relative position of the movable unbalance mass with respect to the fixed unbalance mass is changed and fixed. The selected adjustment may then no longer change during operation.

Disclosure of Invention

The object of the invention is therefore to further develop a vibrator of the type mentioned above in order to avoid excessive tamping of the ground in stable operation on the basis of strong vertical vibrations, so that the operator or the ground to be tamped is not subjected to strong horizontal vibrations in the reverse ram.

According to the invention, this object is achieved by a vibrator for use in a soil compacting machine, having two mutually parallel, upright imbalance shafts which are driven in rotation towards each other at equal rotational speeds, wherein each imbalance shaft carries an imbalance mass fixed to the imbalance shaft and an imbalance mass rotating relative to the respective imbalance shaft, wherein each imbalance shaft is additionally provided with an adjusting device for adjusting the relative position of the movable imbalance masses with respect to the imbalance shafts carrying the imbalance masses, wherein the relative position can be adjusted by means of an adjusting device during operation, so that the centrifugal forces generated by the unbalanced mass when the unbalanced shaft rotates are cancelled out overall at each rotational position of the unbalanced shaft, and effecting a change in the relative position such that the value of the total centrifugal force resulting from the unbalanced masses is proportional to the advancing speed of the tamper.

A vibrator according to the invention preferably has two upright imbalance shafts which are parallel to one another and which are driven in rotation in opposite directions at equal rotational speeds and each carry a fixed imbalance mass and an imbalance mass which is movable rotatably relative to the fixed imbalance mass or the respective imbalance shaft. An adjusting device is attached to each imbalance shaft, by means of which the relative position of the respective movable imbalance mass relative to the respective imbalance shaft carrying the imbalance mass can be adjusted. According to the invention, the relative position of the movable unbalance mass with respect to the unbalance shaft carrying the unbalance mass can be adjusted by means of an adjusting device, the centrifugal forces generated by the unbalance mass when the unbalance mass rotates being cancelled out overall at each rotational position of the unbalance shaft. This means that: although each unbalanced mass pair generates a centrifugal force on itself; but the centrifugal forces are adjusted to be balanced in direction and quantity in sum. Although the unbalanced shaft is rotating, the vibrator does not generate vibration in such an operating state (steady operation).

This way, the situation is achieved in a particularly advantageous manner: the magnitude of the resultant total centrifugal force, i.e., the vibration intensity, is adjusted to depend on the advancing speed of the vibrating plate. If the speed is reduced, the effective centrifugal force is also reduced in the corresponding relationship until the machine is in steady operation, at which point there is no resultant total centrifugal force and therefore no vibration anymore. A very uniform energy is achieved in this way into the ground through the area to be compacted.

In a special embodiment of the invention, the relative position on each imbalance shaft is adjusted such that the centrifugal forces of the imbalance masses carried by the imbalance shaft cancel each other out in each rotational position of the imbalance shaft. This means that: in operation with only one unbalanced shaft, a relative position can be reached in which no vibration effect is present.

In order to achieve the forward movement of the soil compacting machine as in the known devices, in a preferred embodiment of the invention the relative positions are varied such that the centrifugal forces of the unbalanced masses no longer cancel out, but such that a resultant total centrifugal force has a horizontal component. Thereby, as is well known in the art, a forward movement of the vibrating plate is caused.

In the change of direction from a forward movement back to a backward movement, the above-mentioned stable operating position is introduced in a transitional manner, in which no vibrations have an effect on the ground. Thus, undesired vertical or horizontal oscillations can also be avoided in the direction change of the reversal point. Since the adjustment of the moving unbalance masses is already sufficient, in order to generate a resultant centrifugal force with the desired direction and magnitude, in a preferred embodiment, as is the case with the vibrator described in DE10038206a1, it is not required that the phases of the unbalance axes are changed relative to one another.

The concept of "unbalanced mass" is referred to abstractly in this description. It goes without saying that the unbalanced masses can of course also consist of a plurality of unbalanced elements, which are distributed over the respective unbalanced shafts.

Drawings

The above and other advantages and features of the present invention are described in detail below with the aid of the accompanying drawings. Wherein:

FIG. 1 shows a top cross-sectional view taken through a vibrator of the present invention in a stable position; and

fig. 2 shows a schematic cross-sectional view through two imbalance shafts with different rotational positions of the various positions of the imbalance masses.

Detailed Description

As described above, the known vibrators have various patterns. As described in DE19943391a1, a so-called "phasing device" (i.e., an adjusting device for adjusting the relative position of the unbalanced mass and the unbalanced shaft) is known. A detailed description of the vibrator is not necessary, since the invention does not relate to a detailed and concrete structure of a certain vibrator or a certain adjusting device, but more particularly to a relative position (phase) which is particularly suitable for this but hitherto unknown.

However, the construction of a vibrator according to the present invention will be briefly described with reference to fig. 1.

Two imbalance shafts 2, 3 are rotatably mounted in the housing 1, wherein the imbalance shaft 2 is driven in rotation by a drive, not shown.

The imbalance shaft 2 carries imbalance elements 4 and 5, which are fixedly connected to the imbalance shaft 2 to form a fixed imbalance mass.

Furthermore, a rotationally movable imbalance mass 6 is arranged on the imbalance shaft 2, which imbalance mass is rotatable relative to the imbalance shaft 2 via a hub 7 and bearings 8.

The relative position between the moving unbalanced mass 6 and the unbalanced shaft 2 is determined by means of an adjusting device 9. The operating principle of such adjustment devices has long been known, for example, from DE10038206a 1. The adjusting device 9 has a piston 10 which is adjusted essentially hydraulically in the axial direction and which can be moved back and forth in the axial direction in a hollow region of the imbalance shaft 2. The piston 10 has a transverse pin 11 which penetrates into two longitudinal grooves formed in the wall of the imbalance shaft 2 and engages into a helical groove formed on the inside of the hub 7. When the piston 10 and the transverse pin 11 are adjusted in the axial direction, the hub 7 and the movable imbalance mass 6 carried by it rotate relative to the imbalance shaft 2.

The unbalanced shaft 2 also carries a gear wheel 14 which meshes with a gear wheel 15 provided on the unbalanced shaft 3. The rotation of the driven imbalance shaft 2 is transmitted via the gears 14 and 15 to the imbalance shaft 3 in a form-fitting manner, which rotate in opposite directions at the same rotational speed.

The imbalance shaft 3 carries two imbalance elements in the same way as the imbalance shaft 2, which together form a fixed imbalance mass. Furthermore, a rotationally movable imbalance mass 18 is arranged on the imbalance shaft 3, the relative position of which with respect to the imbalance shaft 3 is adjusted by means of an adjusting device 19. Since the adjusting device 19 has the same configuration as the adjusting device 9, a detailed description thereof will not be given.

The position of the unbalanced mass shown in the sectional view of fig. 1 corresponds to a relative position according to the invention in which the centrifugal forces generated by the individual unbalanced masses or unbalanced elements cancel out in their entirety (stable position). This means that: the effects of the unbalance elements 4, 5 or 16, 17 on the one hand and the unbalance of the moving unbalance masses 6, 18 on the other hand are identical in number but must be opposite.

The associated mr values (mass m × radius r of the center of gravity of the unbalanced mass) must be correspondingly corrected to one another.

As a result, the rotation of the unbalance shafts 2 and 3 can be carried out without an unbalance acting outwards and vibrations resulting therefrom. When adjusting the movable unbalance masses 6, 18, however, this state of balance can be cancelled by the adjusting devices 9, 19, so that the desired vertical and horizontal vibrations can be generated for soil compacting.

The different relative positions and the resulting vibration states are shown in fig. 2. Fig. 2 shows a particularly schematic side view from the right in fig. 1.

The hatched half circles correspond to the movable, i.e. adjustable, unbalance masses 6, 18, while the half circles not shown in hatched form correspond to the unbalance masses 4, 5 and 16, 17 fixed relative to the unbalance shafts 2, 3, as shown in the area of the blocks of fig. 2 where a) and "steady operation" intersect.

The state shown in fig. 1 can be traced back to the heading "steady operation" of line a) of fig. 2. The direction of rotation of the imbalance shafts 2, 3 and the associated imbalance masses is indicated by curved arrows. The stable unbalance masses 4, 5 or 16, 17 are always opposite the movable unbalance masses 6, 18.

In rows a) to d) different rotation states of the imbalance shafts 2, 3 are shown, each time through 90 °. It goes without saying that the direction of rotation of the imbalance shafts 2, 3 is the same each time.

To achieve the forward movement of the vibrating plate (left column in fig. 2), the movable unbalance masses 6, 18 are rotated relative to the fixed unbalance masses 4, 5 or 16, 17.

In the example shown, the movable unbalance mass 6 is rotated through 90 ° relative to the fixed unbalance masses 4, 5 and the unbalance shaft 2. Furthermore, the movable unbalance mass 18 is rotated through 90 ° in the same direction as the movable unbalance mass 6 relative to the fixed unbalance masses 16, 17 on the unbalance shaft 3. The corresponding state is shown in a) of the "run ahead" column of fig. 2. Here, different rotation states of the imbalance shafts 2, 3 are shown under a) to d) in the "forward travel" column.

It can be seen that: the centrifugal forces due to the unbalanced masses 4, 5 on the one hand and the unbalanced masses 6 or 16, 17 and 18 on the other hand are no longer balanced as in the case of steady vibrations. Instead, the centrifugal forces are superimposed so as to give a resultant force towards the upper left, which corresponds to the forward direction, shown in a) of fig. 2.

In c) of fig. 2, a corresponding downward-to-right reaction occurs. In this case, the vibrating plate is supported on the ground, and the vibration energy is introduced into the ground.

The backward movement of the vibrating plate (to the right in fig. 2) is shown in the right column of fig. 2. Wherein the movable unbalance masses 6 and 18 are rotated by 90 ° relative to the unbalance shafts 2, 3 carrying them, in a direction opposite to the forward direction relative to the stable position, as can be seen in the "run-back" column of a) of fig. 2.

Thus, as shown in the "backward travel" column of fig. a) and c), the back-and-forth oscillation of the vibrating plate up to the right or down to the left is shown by the straight arrows, which is combined in a backward travel movement.

The positions of the unbalanced masses shown in fig. 2 are extreme positions. Depending on the design of the adjusting devices 9, 19, any intermediate position, i.e. other adjustment angles than 90 °, can also be achieved, so that a continuous change between forward, steady and backward operation is possible.

For the adjusting devices 9, 19, on the one hand, the known means, such as hydraulic control, electric motors, electromechanical actuators, etc., can be resorted to, or, in a simplified embodiment, the control of the movable unbalance masses can also be realized by means of simple tension and compression cables, the unbalance masses being controlled by the operator by means of a common sensor, whereby considerable costs can also be saved in the simplified vibrating plate.

In order to achieve a precise change between the individual operating states, the relative positions can be adjusted synchronously by the adjusting devices 9, 19. In some cases, it is also possible to achieve individual adjustment of the movable imbalance masses without forced synchronization.

The continuous change between forward and backward operation can be used to introduce a stable mode of operation without generating vibrations, which can adapt the amount of the resultant centrifugal force and the vibrations acting thereon, which are proportional to the speed of movement of the vibrating plate. The slower the vibrating plate is moving, the lower the resultant centrifugal force until the vibrating plate is stable, for example, at the return steering point no more vibration is introduced into the ground. This direct relationship can be derived from the construction of the vibrator according to the invention without having to employ expensive control measures.

It goes without saying that other relative positions than those shown in fig. 2 can also be introduced with the vibrator of the invention. In a corresponding configuration of the adjusting devices 9, 19, for example, a relative position can be achieved in which strong horizontal vibrations occur in the steady state of the vibrating plate, although vertical vibrations are not present, as described in DE19943391a 1.

The invention illustrates an example of a vibrator according to fig. 1. Of course, the principle on which the invention is based can also be transferred to other vibrators, for example having a plurality of movable unbalance masses or another number of unbalance shafts.

Claims (8)

1. A vibrator for use in a soil compacting machine, having two mutually parallel, upright imbalance shafts (2, 3) which are driven in rotation in opposite directions at equal rotational speeds, wherein each imbalance shaft (2, 3) carries an imbalance mass (4, 5; 16, 17) which is fixed to the imbalance shaft and an imbalance mass (6, 18) which is movable in rotation relative to the respective imbalance shaft, wherein each imbalance shaft (2, 3) is assigned an adjusting device (9, 19) for adjusting the relative position of the movable imbalance masses (6, 18) relative to the imbalance shafts (2, 3) carrying the imbalance masses, characterized in that,

the relative position can be adjusted during operation by means of an adjusting device (9, 19) in such a way that the centrifugal forces generated by the unbalanced masses (4, 5; 16, 17; 6, 18) during rotation of the unbalanced shafts (2, 3) are cancelled out in their entirety at each rotational position of the unbalanced shafts (2, 3), and

the change in relative position is carried out such that the value of the total centrifugal force resulting from the unbalanced masses is proportional to the advancing speed of the tamper.

2. A vibrator according to claim 1, characterized in that, in order to achieve a horizontal first direction of advance of the tamper, the relative positions are changed so that the centrifugal forces of the unbalanced masses do not cancel each other out, but the total centrifugal force resulting from the centrifugal forces has a horizontal component.

3. A vibrator according to any of claims 1-2, characterized in that the change of relative position is performed continuously.

4. A vibrator according to any one of claims 1-3, characterized in that the unbalance shafts (2, 3) are coupled to each other rotatably in shape towards each other.

5. A vibrator according to any of claims 1-4, characterized in that the phases of the unbalance shafts (2, 3) do not change from each other.

6. A vibrator according to any of claims 1-5, characterized in that the adjustment of the relative position is performed synchronously by means of adjusting means (9, 19) on the unbalance shafts (2, 3).

7. A vibrator according to any of claims 1-6, characterized in that the adjustment means (9, 19) are operated electrically, hydraulically, pneumatically or mechanically.

8. A vibrator according to any of claims 1-7, characterized in that at least a part of the unbalanced mass is formed by a number of unbalanced members (4, 5; 16, 17).